Rewrite extension checking.

Two big changes:

 1. If you're missing some functionality, Movit will now tell you
    on stderr what you're missing. (We might suppress this later
    if it turns out that people want to init_movit() but are actually
    fine with it failing.)
 2. Use a table instead of repeated if-then logic, since this started
    to become a bit messy after we added OpenGL-version-equivalence
    checks.

diff --git a/init.cpp b/init.cpp
index c37614e4c58de3e3be37ea93f804e2aeace978ea..a7bd1e3ea5d4e247722c04f3d1a6d1aabd2b33a4 100644 (file)
--- a/init.cpp
+++ b/init.cpp
@@ -278,6 +278,33 @@ void measure_roundoff_problems()
        check_error();
 }
 
+struct RequiredExtension {
+       int min_equivalent_gl_version;
+       const char extension_name[64];
+};
+const RequiredExtension required_extensions[] = {
+       // We fundamentally need FBOs and floating-point textures.
+       // FBOs are covered by OpenGL 1.5, and are not an extension there.
+       // Floating-point textures are part of OpenGL 3.0 and newer.
+       { 15, "GL_ARB_framebuffer_object" },
+       { 30, "GL_ARB_texture_float" },
+
+       // We assume that we can use non-power-of-two textures without restrictions.
+       { 20, "GL_ARB_texture_non_power_of_two" },
+
+       // We also need GLSL fragment shaders.
+       { 20, "GL_ARB_fragment_shader" },
+       { 20, "GL_ARB_shading_language_100" },
+
+       // FlatInput and YCbCrInput uses PBOs. (They could in theory do without,
+       // but no modern card would really not provide it.)
+       { 21, "GL_ARB_pixel_buffer_object" },
+
+       // ResampleEffect uses RG textures to encode a two-component LUT.
+       // We also need GL_R several places, for single-channel input.
+       { 30, "GL_ARB_texture_rg" },
+};
+
 bool check_extensions()
 {
        // GLES generally doesn't use extensions as actively as desktop OpenGL.
@@ -287,37 +314,34 @@ bool check_extensions()
                if (epoxy_gl_version() >= 30) {
                        movit_srgb_textures_supported = true;
                        movit_shader_rounding_supported = true;
+                       return true;
                } else {
+                       fprintf(stderr, "Movit system requirements: GLES version %.1f is too old (GLES 3.0 needed).\n",
+                               0.1f * epoxy_gl_version());
+                       fprintf(stderr, "Movit initialization failed.\n");
                        return false;
                }
        }
 
-       // We fundamentally need FBOs and floating-point textures.
-       // FBOs are covered by OpenGL 1.5, and are not an extension there.
-       // Floating-point textures are part of OpenGL 3.0 and newer.
-       if (epoxy_gl_version() < 15 &&
-           !epoxy_has_gl_extension("GL_ARB_framebuffer_object")) return false;
-       if (epoxy_gl_version() < 30 &&
-           !epoxy_has_gl_extension("GL_ARB_texture_float")) return false;
-
-       // We assume that we can use non-power-of-two textures without restrictions.
-       if (epoxy_gl_version() < 20 &&
-           !epoxy_has_gl_extension("GL_ARB_texture_non_power_of_two")) return false;
-
-       // We also need GLSL fragment shaders.
-       if (epoxy_gl_version() < 20) {
-               if (!epoxy_has_gl_extension("GL_ARB_fragment_shader")) return false;
-               if (!epoxy_has_gl_extension("GL_ARB_shading_language_100")) return false;
+       // Check all extensions, and output errors for the ones that we are missing.
+       bool all_ok = true;
+       int gl_version = epoxy_gl_version();
+
+       for (unsigned i = 0; i < sizeof(required_extensions) / sizeof(required_extensions[0]); ++i) {
+               if (gl_version < required_extensions[i].min_equivalent_gl_version &&
+                   !epoxy_has_gl_extension(required_extensions[i].extension_name)) {
+                       fprintf(stderr, "Movit system requirements: Needs extension '%s' or at least OpenGL version %.1f (has version %.1f)\n",
+                               required_extensions[i].extension_name,
+                               0.1f * required_extensions[i].min_equivalent_gl_version,
+                               0.1f * gl_version);
+                       all_ok = false;
+               }
        }
 
-       // FlatInput and YCbCrInput uses PBOs. (They could in theory do without,
-       // but no modern card would really not provide it.)
-       if (epoxy_gl_version() < 21 &&
-           !epoxy_has_gl_extension("GL_ARB_pixel_buffer_object")) return false;
-
-       // ResampleEffect uses RG textures to encode a two-component LUT.
-       if (epoxy_gl_version() < 30 &&
-           !epoxy_has_gl_extension("GL_ARB_texture_rg")) return false;
+       if (!all_ok) {
+               fprintf(stderr, "Movit initialization failed.\n");
+               return false;
+       }
 
        // sRGB texture decode would be nice, but are not mandatory
        // (GammaExpansionEffect can do the same thing if needed).