Document promise_to_disable_if_enabled.

[nageru-docs] / theme.rst

diff --git a/theme.rst b/theme.rst
index abf7d3be715c90db2c1bb6a74558ef0e0434a5a1..dbfdebe8e684ba302f8fe74498b212bf7775ece1 100644 (file)
--- a/theme.rst
+++ b/theme.rst
@@ -83,6 +83,7 @@ produces a mix of them; Movit's *MixEffect* is exactly what you want here::
   local input1 = scene:add_input()
   input1:display(1)
 
+  -- Note that add_effect returns its input for convenience.
   local mix_effect = scene:add_effect(MixEffect.new(), input0, input1)
   scene:finalize()
 
@@ -183,15 +184,28 @@ directly by the GPU) that instead. The scaling is set up like this::
   -- Or by numerical index:
   input0_scaled:choose(1)  -- Chooses ResizeEffect
 
-Note that add_effect returns its input for convenience. All alternatives must
-have the same amount of inputs, with an exception for IdentityEffect, which can
-coexist with an effect requiring any amount of inputs (if selected, the IdentityEffect
-just passes its first input unchanged).
-
 Actually, add_optional_effect() is just a wrapper around add_effect() with
 IdentityEffect as the other alternative, and disable() is a convenience version of
 choose(IdentityEffect).
 
+All alternatives must
+have the same amount of inputs, with an exception for IdentityEffect, which can
+coexist with an effect requiring any amount of inputs (if selected, the IdentityEffect
+just passes its first input unchanged). Similarly, if you set a parameter with
+set_int() or similar, it must be valid for all alternatives (again excepting
+IdentityEffect); if there is one that can only be used on a certain alternative,
+you must set it directly on the effect::
+
+  local resample_effect = ResampleEffect.new()
+  resample_effect:set_float("zoom_x", 1.0001)  -- Not valid for ResizeEffect.
+   
+  local input0_scaled = scene:add_effect({resample_effect, ResizeEffect.new()})
+  input0_scaled:set_int("width", 1280)  -- Set on both alternatives.
+  input0_scaled:set_int("height", 720)
+
+  -- This is also possible, as choose() returns the chosen effect:
+  input0_scaled:choose(ResampleEffect):set_float("zoom_y", 1.0001)
+
 Actually, more versions are created than you'd immediately expect.
 In particular, the output format for the live output and all previews are
 different (Y'CbCr versus RGBA), which is also handled transparently for you.
@@ -385,6 +399,17 @@ crop is. If so, you can do this::
 
    resample_effect:always_disable_if_disabled(crop_effect)
 
+Also, since Nageru 1.9.1, you can disable an optional effect if a given other
+effect is *enabled*::
+
+   overlay1_effect:promise_to_disable_if_enabled(overlay2_effect)
+   overlay2_effect:promise_to_disable_if_enabled(overlay1_effect)
+
+Note that the latter is a promise from the user, not automatic disabling; since
+it is mostly useful for mutual exclusions, Nageru wouldn't know which of the
+two to disable. (If you violate the promise, you will get an error message at
+runtime.) It can still be useful for reducing the number of alternatives, though.
+
 For more advanced exclusions, you may choose to split up the scenes into several
 distinct ones that you manage yourself; indeed, before Nageru 1.9.0, that was
 the only option. At some point, however, you may choose to simply accept the
@@ -482,3 +507,22 @@ or frame rate:
 You can use this either for display purposes, or for choosing the right
 effect alternatives. In particular, you may want to disable scaling if
 the frame is already of the correct resolution.
+
+
+Overriding the status line
+--------------------------
+
+Some users may wish to override the status line, e.g. with recording time.
+If so, it is possible (since Nageru 1.9.1) to declare a function **format_status_line**::
+
+  function format_status_line(disk_space_text, file_length_seconds)
+    if file_length_seconds > 86400.0 then
+      return "Time to make a new segment"
+    else
+      return "Disk space left: " .. disk_space_text
+    end
+  end
+
+As demonstrated, it is given the disk space text (that would normally
+be there), and the length of the current recording file in seconds.
+HTML is supported.