]> git.sesse.net Git - nageru/blob - midi_mapping_dialog.cpp
Fix an issue where the mixer lagging too much behind CEF would cause us to display...
[nageru] / midi_mapping_dialog.cpp
1 #include "midi_mapping_dialog.h"
2
3 #include <assert.h>
4 #include <google/protobuf/descriptor.h>
5 #include <google/protobuf/message.h>
6 #include <QComboBox>
7 #include <QDialogButtonBox>
8 #include <QFileDialog>
9 #include <QMessageBox>
10 #include <QPushButton>
11 #include <QSpinBox>
12 #include <QStringList>
13 #include <QTreeWidget>
14 #include <stdio.h>
15 #include <algorithm>
16 #include <cstddef>
17 #include <functional>
18 #include <limits>
19 #include <string>
20
21 #include "midi_mapper.h"
22 #include "midi_mapping.pb.h"
23 #include "post_to_main_thread.h"
24 #include "ui_midi_mapping.h"
25
26 class QObject;
27
28 using namespace google::protobuf;
29 using namespace std;
30
31 vector<MIDIMappingDialog::Control> per_bus_controllers = {
32         { "Treble",                   MIDIMappingBusProto::kTrebleFieldNumber, MIDIMappingProto::kTrebleBankFieldNumber },
33         { "Mid",                      MIDIMappingBusProto::kMidFieldNumber,    MIDIMappingProto::kMidBankFieldNumber },
34         { "Bass",                     MIDIMappingBusProto::kBassFieldNumber,   MIDIMappingProto::kBassBankFieldNumber },
35         { "Gain",                     MIDIMappingBusProto::kGainFieldNumber,   MIDIMappingProto::kGainBankFieldNumber },
36         { "Compressor threshold",     MIDIMappingBusProto::kCompressorThresholdFieldNumber,
37                                       MIDIMappingProto::kCompressorThresholdBankFieldNumber},
38         { "Fader",                    MIDIMappingBusProto::kFaderFieldNumber,  MIDIMappingProto::kFaderBankFieldNumber }
39 };
40 vector<MIDIMappingDialog::Control> per_bus_buttons = {
41         { "Toggle mute",              MIDIMappingBusProto::kToggleMuteFieldNumber,
42                                       MIDIMappingProto::kToggleMuteBankFieldNumber },
43         { "Toggle locut",             MIDIMappingBusProto::kToggleLocutFieldNumber,
44                                       MIDIMappingProto::kToggleLocutBankFieldNumber },
45         { "Togle auto gain staging",  MIDIMappingBusProto::kToggleAutoGainStagingFieldNumber,
46                                       MIDIMappingProto::kToggleAutoGainStagingBankFieldNumber },
47         { "Togle compressor",         MIDIMappingBusProto::kToggleCompressorFieldNumber,
48                                       MIDIMappingProto::kToggleCompressorBankFieldNumber },
49         { "Clear peak",               MIDIMappingBusProto::kClearPeakFieldNumber,
50                                       MIDIMappingProto::kClearPeakBankFieldNumber }
51 };
52 vector<MIDIMappingDialog::Control> per_bus_lights = {
53         { "Is muted",                 MIDIMappingBusProto::kIsMutedFieldNumber, 0 },
54         { "Locut is on",              MIDIMappingBusProto::kLocutIsOnFieldNumber, 0 },
55         { "Auto gain staging is on",  MIDIMappingBusProto::kAutoGainStagingIsOnFieldNumber, 0 },
56         { "Compressor is on",         MIDIMappingBusProto::kCompressorIsOnFieldNumber, 0 },
57         { "Bus has peaked",           MIDIMappingBusProto::kHasPeakedFieldNumber, 0 }
58 };
59 vector<MIDIMappingDialog::Control> global_controllers = {
60         { "Locut cutoff",             MIDIMappingBusProto::kLocutFieldNumber,  MIDIMappingProto::kLocutBankFieldNumber },
61         { "Limiter threshold",        MIDIMappingBusProto::kLimiterThresholdFieldNumber,
62                                       MIDIMappingProto::kLimiterThresholdBankFieldNumber },
63         { "Makeup gain",              MIDIMappingBusProto::kMakeupGainFieldNumber,
64                                       MIDIMappingProto::kMakeupGainBankFieldNumber }
65 };
66 vector<MIDIMappingDialog::Control> global_buttons = {
67         { "Previous bank",            MIDIMappingBusProto::kPrevBankFieldNumber, 0 },
68         { "Next bank",                MIDIMappingBusProto::kNextBankFieldNumber, 0 },
69         { "Select bank 1",            MIDIMappingBusProto::kSelectBank1FieldNumber, 0 },
70         { "Select bank 2",            MIDIMappingBusProto::kSelectBank2FieldNumber, 0 },
71         { "Select bank 3",            MIDIMappingBusProto::kSelectBank3FieldNumber, 0 },
72         { "Select bank 4",            MIDIMappingBusProto::kSelectBank4FieldNumber, 0 },
73         { "Select bank 5",            MIDIMappingBusProto::kSelectBank5FieldNumber, 0 },
74         { "Toggle limiter",           MIDIMappingBusProto::kToggleLimiterFieldNumber, MIDIMappingProto::kToggleLimiterBankFieldNumber },
75         { "Toggle auto makeup gain",  MIDIMappingBusProto::kToggleAutoMakeupGainFieldNumber, MIDIMappingProto::kToggleAutoMakeupGainBankFieldNumber }
76 };
77 vector<MIDIMappingDialog::Control> global_lights = {
78         { "Bank 1 is selected",       MIDIMappingBusProto::kBank1IsSelectedFieldNumber, 0 },
79         { "Bank 2 is selected",       MIDIMappingBusProto::kBank2IsSelectedFieldNumber, 0 },
80         { "Bank 3 is selected",       MIDIMappingBusProto::kBank3IsSelectedFieldNumber, 0 },
81         { "Bank 4 is selected",       MIDIMappingBusProto::kBank4IsSelectedFieldNumber, 0 },
82         { "Bank 5 is selected",       MIDIMappingBusProto::kBank5IsSelectedFieldNumber, 0 },
83         { "Limiter is on",            MIDIMappingBusProto::kLimiterIsOnFieldNumber, 0 },
84         { "Auto makeup gain is on",   MIDIMappingBusProto::kAutoMakeupGainIsOnFieldNumber, 0 },
85 };
86
87 namespace {
88
89 int get_bank(const MIDIMappingProto &mapping_proto, int bank_field_number, int default_value)
90 {
91         const FieldDescriptor *bank_descriptor = mapping_proto.GetDescriptor()->FindFieldByNumber(bank_field_number);
92         const Reflection *reflection = mapping_proto.GetReflection();
93         if (!reflection->HasField(mapping_proto, bank_descriptor)) {
94                 return default_value;
95         }
96         return reflection->GetInt32(mapping_proto, bank_descriptor);
97 }
98
99 int get_controller_mapping(const MIDIMappingProto &mapping_proto, size_t bus_idx, int field_number, int default_value)
100 {
101         if (bus_idx >= size_t(mapping_proto.bus_mapping_size())) {
102                 return default_value;
103         }
104
105         const MIDIMappingBusProto &bus_mapping = mapping_proto.bus_mapping(bus_idx);
106         const FieldDescriptor *descriptor = bus_mapping.GetDescriptor()->FindFieldByNumber(field_number);
107         const Reflection *bus_reflection = bus_mapping.GetReflection();
108         if (!bus_reflection->HasField(bus_mapping, descriptor)) {
109                 return default_value;
110         }
111         const MIDIControllerProto &controller_proto =
112                 static_cast<const MIDIControllerProto &>(bus_reflection->GetMessage(bus_mapping, descriptor));
113         return controller_proto.controller_number();
114 }
115
116 int get_button_mapping(const MIDIMappingProto &mapping_proto, size_t bus_idx, int field_number, int default_value)
117 {
118         if (bus_idx >= size_t(mapping_proto.bus_mapping_size())) {
119                 return default_value;
120         }
121
122         const MIDIMappingBusProto &bus_mapping = mapping_proto.bus_mapping(bus_idx);
123         const FieldDescriptor *descriptor = bus_mapping.GetDescriptor()->FindFieldByNumber(field_number);
124         const Reflection *bus_reflection = bus_mapping.GetReflection();
125         if (!bus_reflection->HasField(bus_mapping, descriptor)) {
126                 return default_value;
127         }
128         const MIDIButtonProto &bus_proto =
129                 static_cast<const MIDIButtonProto &>(bus_reflection->GetMessage(bus_mapping, descriptor));
130         return bus_proto.note_number();
131 }
132
133 int get_light_mapping(const MIDIMappingProto &mapping_proto, size_t bus_idx, int field_number, int default_value)
134 {
135         if (bus_idx >= size_t(mapping_proto.bus_mapping_size())) {
136                 return default_value;
137         }
138
139         const MIDIMappingBusProto &bus_mapping = mapping_proto.bus_mapping(bus_idx);
140         const FieldDescriptor *descriptor = bus_mapping.GetDescriptor()->FindFieldByNumber(field_number);
141         const Reflection *bus_reflection = bus_mapping.GetReflection();
142         if (!bus_reflection->HasField(bus_mapping, descriptor)) {
143                 return default_value;
144         }
145         const MIDILightProto &bus_proto =
146                 static_cast<const MIDILightProto &>(bus_reflection->GetMessage(bus_mapping, descriptor));
147         return bus_proto.note_number();
148 }
149
150 }  // namespace
151
152 MIDIMappingDialog::MIDIMappingDialog(MIDIMapper *mapper)
153         : ui(new Ui::MIDIMappingDialog),
154           mapper(mapper)
155 {
156         ui->setupUi(this);
157
158         const MIDIMappingProto mapping_proto = mapper->get_current_mapping();  // Take a copy.
159         old_receiver = mapper->set_receiver(this);
160
161         QStringList labels;
162         labels << "";
163         labels << "Controller bank";
164         for (unsigned bus_idx = 0; bus_idx < num_buses; ++bus_idx) {
165                 char buf[256];
166                 snprintf(buf, sizeof(buf), "Bus %d", bus_idx + 1);
167                 labels << buf;
168         }
169         labels << "";
170         ui->treeWidget->setColumnCount(num_buses + 3);
171         ui->treeWidget->setHeaderLabels(labels);
172
173         add_controls("Per-bus controllers", ControlType::CONTROLLER, SpinnerGroup::PER_BUS_CONTROLLERS, mapping_proto, per_bus_controllers);
174         add_controls("Per-bus buttons", ControlType::BUTTON, SpinnerGroup::PER_BUS_BUTTONS, mapping_proto, per_bus_buttons);
175         add_controls("Per-bus lights", ControlType::LIGHT, SpinnerGroup::PER_BUS_LIGHTS, mapping_proto, per_bus_lights);
176         add_controls("Global controllers", ControlType::CONTROLLER, SpinnerGroup::GLOBAL_CONTROLLERS, mapping_proto, global_controllers);
177         add_controls("Global buttons", ControlType::BUTTON, SpinnerGroup::GLOBAL_BUTTONS, mapping_proto, global_buttons);
178         add_controls("Global lights", ControlType::LIGHT, SpinnerGroup::GLOBAL_LIGHTS, mapping_proto, global_lights);
179         fill_controls_from_mapping(mapping_proto);
180
181         // Auto-resize every column but the last.
182         for (unsigned column_idx = 0; column_idx < num_buses + 3; ++column_idx) {
183                 ui->treeWidget->resizeColumnToContents(column_idx);
184         }
185
186         connect(ui->guess_bus_button, &QPushButton::clicked,
187                 bind(&MIDIMappingDialog::guess_clicked, this, false));
188         connect(ui->guess_group_button, &QPushButton::clicked,
189                 bind(&MIDIMappingDialog::guess_clicked, this, true));
190         connect(ui->ok_cancel_buttons, &QDialogButtonBox::accepted, this, &MIDIMappingDialog::ok_clicked);
191         connect(ui->ok_cancel_buttons, &QDialogButtonBox::rejected, this, &MIDIMappingDialog::cancel_clicked);
192         connect(ui->save_button, &QPushButton::clicked, this, &MIDIMappingDialog::save_clicked);
193         connect(ui->load_button, &QPushButton::clicked, this, &MIDIMappingDialog::load_clicked);
194
195         update_guess_button_state();
196 }
197
198 MIDIMappingDialog::~MIDIMappingDialog()
199 {
200         mapper->set_receiver(old_receiver);
201         mapper->refresh_highlights();
202 }
203
204 bool MIDIMappingDialog::eventFilter(QObject *obj, QEvent *event)
205 {
206         if (event->type() == QEvent::FocusIn ||
207             event->type() == QEvent::FocusOut) {
208                 // We ignore the guess buttons themselves; it should be allowed
209                 // to navigate from a spinner to focus on a button (to click it).
210                 if (obj != ui->guess_bus_button && obj != ui->guess_group_button) {
211                         update_guess_button_state();
212                 }
213         }
214         return false;
215 }
216
217 void MIDIMappingDialog::guess_clicked(bool limit_to_group)
218 {
219         FocusInfo focus = find_focus();
220         if (focus.bus_idx == -1) {
221                 // The guess button probably took the focus away from us.
222                 focus = last_focus;
223         }
224         assert(focus.bus_idx != -1);  // The button should have been disabled.
225         pair<int, int> bus_and_offset = guess_offset(focus.bus_idx, limit_to_group ? focus.spinner_group : SpinnerGroup::ALL_GROUPS);
226         const int source_bus_idx = bus_and_offset.first;
227         const int offset = bus_and_offset.second;
228         assert(source_bus_idx != -1);  // The button should have been disabled.
229
230         for (const auto &field_number_and_spinner : spinners[focus.bus_idx]) {
231                 int field_number = field_number_and_spinner.first;
232                 QSpinBox *spinner = field_number_and_spinner.second.spinner;
233                 SpinnerGroup this_spinner_group = field_number_and_spinner.second.group;
234
235                 if (limit_to_group && this_spinner_group != focus.spinner_group) {
236                         continue;
237                 }
238
239                 assert(spinners[source_bus_idx].count(field_number));
240                 QSpinBox *source_spinner = spinners[source_bus_idx][field_number].spinner;
241                 assert(spinners[source_bus_idx][field_number].group == this_spinner_group);
242
243                 if (source_spinner->value() != -1) {
244                         spinner->setValue(source_spinner->value() + offset);
245                 }
246         }
247
248         // See if we can find a “next” bus to move the focus to.
249         const int next_bus_idx = focus.bus_idx + (focus.bus_idx - source_bus_idx);  // Note: Could become e.g. -1.
250         for (const InstantiatedSpinner &is : controller_spinners) {
251                 if (int(is.bus_idx) == next_bus_idx && is.field_number == focus.field_number) {
252                         is.spinner->setFocus();
253                 }
254         }
255         for (const InstantiatedSpinner &is : button_spinners) {
256                 if (int(is.bus_idx) == next_bus_idx && is.field_number == focus.field_number) {
257                         is.spinner->setFocus();
258                 }
259         }
260         for (const InstantiatedSpinner &is : light_spinners) {
261                 if (int(is.bus_idx) == next_bus_idx && is.field_number == focus.field_number) {
262                         is.spinner->setFocus();
263                 }
264         }
265 }
266
267 void MIDIMappingDialog::ok_clicked()
268 {
269         unique_ptr<MIDIMappingProto> new_mapping = construct_mapping_proto_from_ui();
270         mapper->set_midi_mapping(*new_mapping);
271         mapper->set_receiver(old_receiver);
272         accept();
273 }
274
275 void MIDIMappingDialog::cancel_clicked()
276 {
277         mapper->set_receiver(old_receiver);
278         reject();
279 }
280
281 void MIDIMappingDialog::save_clicked()
282 {
283         unique_ptr<MIDIMappingProto> new_mapping = construct_mapping_proto_from_ui();
284         QString filename = QFileDialog::getSaveFileName(this,
285                 "Save MIDI mapping", QString(), tr("Mapping files (*.midimapping)"));
286         if (!filename.endsWith(".midimapping")) {
287                 filename += ".midimapping";
288         }
289         if (!save_midi_mapping_to_file(*new_mapping, filename.toStdString())) {
290                 QMessageBox box;
291                 box.setText("Could not save mapping to '" + filename + "'. Check that you have the right permissions and try again.");
292                 box.exec();
293         }
294 }
295
296 void MIDIMappingDialog::load_clicked()
297 {
298         QString filename = QFileDialog::getOpenFileName(this,
299                 "Load MIDI mapping", QString(), tr("Mapping files (*.midimapping)"));
300         MIDIMappingProto new_mapping;
301         if (!load_midi_mapping_from_file(filename.toStdString(), &new_mapping)) {
302                 QMessageBox box;
303                 box.setText("Could not load mapping from '" + filename + "'. Check that the file exists, has the right permissions and is valid.");
304                 box.exec();
305                 return;
306         }
307
308         fill_controls_from_mapping(new_mapping);
309 }
310
311 namespace {
312
313 template<class T>
314 T *get_mutable_bus_message(MIDIMappingProto *mapping_proto, unsigned bus_idx, int field_number)
315 {
316         while (size_t(mapping_proto->bus_mapping_size()) <= bus_idx) {
317                 mapping_proto->add_bus_mapping();
318         }
319
320         MIDIMappingBusProto *bus_mapping = mapping_proto->mutable_bus_mapping(bus_idx);
321         const FieldDescriptor *descriptor = bus_mapping->GetDescriptor()->FindFieldByNumber(field_number);
322         const Reflection *bus_reflection = bus_mapping->GetReflection();
323         return static_cast<T *>(bus_reflection->MutableMessage(bus_mapping, descriptor));
324 }
325
326 }  // namespace
327
328 unique_ptr<MIDIMappingProto> MIDIMappingDialog::construct_mapping_proto_from_ui()
329 {
330         unique_ptr<MIDIMappingProto> mapping_proto(new MIDIMappingProto);
331         for (const InstantiatedSpinner &is : controller_spinners) {
332                 const int val = is.spinner->value();
333                 if (val == -1) {
334                         continue;
335                 }
336
337                 MIDIControllerProto *controller_proto =
338                         get_mutable_bus_message<MIDIControllerProto>(mapping_proto.get(), is.bus_idx, is.field_number);
339                 controller_proto->set_controller_number(val);
340         }
341         for (const InstantiatedSpinner &is : button_spinners) {
342                 const int val = is.spinner->value();
343                 if (val == -1) {
344                         continue;
345                 }
346
347                 MIDIButtonProto *button_proto =
348                         get_mutable_bus_message<MIDIButtonProto>(mapping_proto.get(), is.bus_idx, is.field_number);
349                 button_proto->set_note_number(val);
350         }
351         for (const InstantiatedSpinner &is : light_spinners) {
352                 const int val = is.spinner->value();
353                 if (val == -1) {
354                         continue;
355                 }
356
357                 MIDILightProto *light_proto =
358                         get_mutable_bus_message<MIDILightProto>(mapping_proto.get(), is.bus_idx, is.field_number);
359                 light_proto->set_note_number(val);
360         }
361         int highest_bank_used = 0;  // 1-indexed.
362         for (const InstantiatedComboBox &ic : bank_combo_boxes) {
363                 const int val = ic.combo_box->currentIndex();
364                 highest_bank_used = std::max(highest_bank_used, val);
365                 if (val == 0) {
366                         continue;
367                 }
368
369                 const FieldDescriptor *descriptor = mapping_proto->GetDescriptor()->FindFieldByNumber(ic.field_number);
370                 const Reflection *bus_reflection = mapping_proto->GetReflection();
371                 bus_reflection->SetInt32(mapping_proto.get(), descriptor, val - 1);
372         }
373         mapping_proto->set_num_controller_banks(highest_bank_used);
374         return mapping_proto;
375 }
376
377 void MIDIMappingDialog::add_bank_selector(QTreeWidgetItem *item, const MIDIMappingProto &mapping_proto, int bank_field_number)
378 {
379         if (bank_field_number == 0) {
380                 return;
381         }
382         QComboBox *bank_selector = new QComboBox(this);
383         bank_selector->addItems(QStringList() << "" << "Bank 1" << "Bank 2" << "Bank 3" << "Bank 4" << "Bank 5");
384         bank_selector->setAutoFillBackground(true);
385
386         bank_combo_boxes.push_back(InstantiatedComboBox{ bank_selector, bank_field_number });
387
388         ui->treeWidget->setItemWidget(item, 1, bank_selector);
389 }
390
391 void MIDIMappingDialog::add_controls(const string &heading,
392                                      MIDIMappingDialog::ControlType control_type,
393                                      MIDIMappingDialog::SpinnerGroup spinner_group,
394                                      const MIDIMappingProto &mapping_proto,
395                                      const vector<MIDIMappingDialog::Control> &controls)
396 {
397         QTreeWidgetItem *heading_item = new QTreeWidgetItem(ui->treeWidget);
398         heading_item->setText(0, QString::fromStdString(heading));
399         heading_item->setFirstColumnSpanned(true);
400         heading_item->setExpanded(true);
401         for (const Control &control : controls) {
402                 QTreeWidgetItem *item = new QTreeWidgetItem(heading_item);
403                 heading_item->addChild(item);
404                 add_bank_selector(item, mapping_proto, control.bank_field_number);
405                 item->setText(0, QString::fromStdString(control.label + "   "));
406
407                 for (unsigned bus_idx = 0; bus_idx < num_buses; ++bus_idx) {
408                         QSpinBox *spinner = new QSpinBox(this);
409                         spinner->setRange(-1, 127);
410                         spinner->setAutoFillBackground(true);
411                         spinner->setSpecialValueText("\u200d");  // Zero-width joiner (ie., empty).
412                         spinner->installEventFilter(this);  // So we know when the focus changes.
413                         ui->treeWidget->setItemWidget(item, bus_idx + 2, spinner);
414
415                         if (control_type == ControlType::CONTROLLER) {
416                                 controller_spinners.push_back(InstantiatedSpinner{ spinner, bus_idx, spinner_group, control.field_number });
417                         } else if (control_type == ControlType::BUTTON) {
418                                 button_spinners.push_back(InstantiatedSpinner{ spinner, bus_idx, spinner_group, control.field_number });
419                         } else {
420                                 assert(control_type == ControlType::LIGHT);
421                                 light_spinners.push_back(InstantiatedSpinner{ spinner, bus_idx, spinner_group, control.field_number });
422                         }
423                         spinners[bus_idx][control.field_number] = SpinnerAndGroup{ spinner, spinner_group };
424                         connect(spinner, static_cast<void(QSpinBox::*)(int)>(&QSpinBox::valueChanged),
425                                 bind(&MIDIMappingDialog::update_guess_button_state, this));
426                 }
427         }
428         ui->treeWidget->addTopLevelItem(heading_item);
429 }
430
431 void MIDIMappingDialog::fill_controls_from_mapping(const MIDIMappingProto &mapping_proto)
432 {
433         for (const InstantiatedSpinner &is : controller_spinners) {
434                 is.spinner->setValue(get_controller_mapping(mapping_proto, is.bus_idx, is.field_number, -1));
435         }
436         for (const InstantiatedSpinner &is : button_spinners) {
437                 is.spinner->setValue(get_button_mapping(mapping_proto, is.bus_idx, is.field_number, -1));
438         }
439         for (const InstantiatedSpinner &is : light_spinners) {
440                 is.spinner->setValue(get_light_mapping(mapping_proto, is.bus_idx, is.field_number, -1));
441         }
442         for (const InstantiatedComboBox &ic : bank_combo_boxes) {
443                 ic.combo_box->setCurrentIndex(get_bank(mapping_proto, ic.field_number, -1) + 1);
444         }
445 }
446
447 void MIDIMappingDialog::controller_changed(unsigned controller)
448 {
449         post_to_main_thread([=]{
450                 for (const InstantiatedSpinner &is : controller_spinners) {
451                         if (is.spinner->hasFocus()) {
452                                 is.spinner->setValue(controller);
453                                 is.spinner->selectAll();
454                         }
455                 }
456         });
457 }
458
459 void MIDIMappingDialog::note_on(unsigned note)
460 {
461         post_to_main_thread([=]{
462                 for (const InstantiatedSpinner &is : button_spinners) {
463                         if (is.spinner->hasFocus()) {
464                                 is.spinner->setValue(note);
465                                 is.spinner->selectAll();
466                         }
467                 }
468                 for (const InstantiatedSpinner &is : light_spinners) {
469                         if (is.spinner->hasFocus()) {
470                                 is.spinner->setValue(note);
471                                 is.spinner->selectAll();
472                         }
473                 }
474         });
475 }
476
477 pair<int, int> MIDIMappingDialog::guess_offset(unsigned bus_idx, MIDIMappingDialog::SpinnerGroup spinner_group)
478 {
479         constexpr pair<int, int> not_found(-1, 0);
480
481         if (bus_is_empty(bus_idx, spinner_group)) {
482                 return not_found;
483         }
484
485         // See if we can find a non-empty bus to source from (prefer from the left).
486         unsigned source_bus_idx;
487         if (bus_idx > 0 && !bus_is_empty(bus_idx - 1, spinner_group)) {
488                 source_bus_idx = bus_idx - 1;
489         } else if (bus_idx < num_buses - 1 && !bus_is_empty(bus_idx + 1, spinner_group)) {
490                 source_bus_idx = bus_idx + 1;
491         } else {
492                 return not_found;
493         }
494
495         // See if we can find a consistent offset.
496         bool found_offset = false;
497         int offset = 0;
498         int minimum_allowed_offset = numeric_limits<int>::min();
499         int maximum_allowed_offset = numeric_limits<int>::max();
500         for (const auto &field_number_and_spinner : spinners[bus_idx]) {
501                 int field_number = field_number_and_spinner.first;
502                 QSpinBox *spinner = field_number_and_spinner.second.spinner;
503                 SpinnerGroup this_spinner_group = field_number_and_spinner.second.group;
504                 assert(spinners[source_bus_idx].count(field_number));
505                 QSpinBox *source_spinner = spinners[source_bus_idx][field_number].spinner;
506                 assert(spinners[source_bus_idx][field_number].group == this_spinner_group);
507
508                 if (spinner_group != SpinnerGroup::ALL_GROUPS &&
509                     spinner_group != this_spinner_group) {
510                         continue;
511                 }
512                 if (spinner->value() == -1) {
513                         if (source_spinner->value() != -1) {
514                                 // If the source value is e.g. 3, offset can't be less than -2 or larger than 124.
515                                 // Otherwise, we'd extrapolate values outside [1..127].
516                                 minimum_allowed_offset = max(minimum_allowed_offset, 1 - source_spinner->value());
517                                 maximum_allowed_offset = min(maximum_allowed_offset, 127 - source_spinner->value());
518                         }
519                         continue;
520                 }
521                 if (source_spinner->value() == -1) {
522                         // The bus has a controller set that the source bus doesn't set.
523                         return not_found;
524                 }
525
526                 int candidate_offset = spinner->value() - source_spinner->value();
527                 if (!found_offset) {
528                         offset = candidate_offset;
529                         found_offset = true;
530                 } else if (candidate_offset != offset) {
531                         return not_found;
532                 }
533         }
534
535         if (!found_offset) {
536                 // Given that the bus wasn't empty, this shouldn't happen.
537                 assert(false);
538                 return not_found;
539         }
540
541         if (offset < minimum_allowed_offset || offset > maximum_allowed_offset) {
542                 return not_found;
543         }
544         return make_pair(source_bus_idx, offset);
545 }
546
547 bool MIDIMappingDialog::bus_is_empty(unsigned bus_idx, SpinnerGroup spinner_group)
548 {
549         for (const auto &field_number_and_spinner : spinners[bus_idx]) {
550                 QSpinBox *spinner = field_number_and_spinner.second.spinner;
551                 SpinnerGroup this_spinner_group = field_number_and_spinner.second.group;
552                 if (spinner_group != SpinnerGroup::ALL_GROUPS &&
553                     spinner_group != this_spinner_group) {
554                         continue;
555                 }
556                 if (spinner->value() != -1) {
557                         return false;
558                 }
559         }
560         return true;
561 }
562
563 void MIDIMappingDialog::update_guess_button_state()
564 {
565         FocusInfo focus = find_focus();
566         if (focus.bus_idx < 0) {
567                 return;
568         }
569         {
570                 pair<int, int> bus_and_offset = guess_offset(focus.bus_idx, SpinnerGroup::ALL_GROUPS);
571                 ui->guess_bus_button->setEnabled(bus_and_offset.first != -1);
572         }
573         {
574                 pair<int, int> bus_and_offset = guess_offset(focus.bus_idx, focus.spinner_group);
575                 ui->guess_group_button->setEnabled(bus_and_offset.first != -1);
576         }
577         last_focus = focus;
578 }
579
580 MIDIMappingDialog::FocusInfo MIDIMappingDialog::find_focus() const
581 {
582         for (const InstantiatedSpinner &is : controller_spinners) {
583                 if (is.spinner->hasFocus()) {
584                         return FocusInfo{ int(is.bus_idx), is.spinner_group, is.field_number };
585                 }
586         }
587         for (const InstantiatedSpinner &is : button_spinners) {
588                 if (is.spinner->hasFocus()) {
589                         return FocusInfo{ int(is.bus_idx), is.spinner_group, is.field_number };
590                 }
591         }
592         for (const InstantiatedSpinner &is : light_spinners) {
593                 if (is.spinner->hasFocus()) {
594                         return FocusInfo{ int(is.bus_idx), is.spinner_group, is.field_number };
595                 }
596         }
597         return FocusInfo{ -1, SpinnerGroup::ALL_GROUPS, -1 };
598 }