cogl: Add a fp32 format for pixel read-back

We will also require GL_OES_texture_half_float and GLES 3.0 to enable
COGL_FEATURE_ID_TEXTURE_HALF_FLOAT. This gives us float types and makes
it possible to read pixels from framebuffers with internal floating
point formats (into float, half is never supported).

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3441>

cogl/cogl/cogl-pixel-format.c

@@ -385,6 +385,20 @@ static const CoglPixelFormatInfo format_info_table[] = {
     .bpp = { 8 },
     .aligned = 1
   },
+  {
+    .cogl_format = COGL_PIXEL_FORMAT_RGBA_FP_32323232,
+    .format_str = "RGBA_FP_32323232",
+    .n_planes = 1,
+    .bpp = { 16 },
+    .aligned = 1
+  },
+  {
+    .cogl_format = COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE,
+    .format_str = "RGBA_FP_32323232_PRE",
+    .n_planes = 1,
+    .bpp = { 16 },
+    .aligned = 1
+  },
   {
     .cogl_format = COGL_PIXEL_FORMAT_DEPTH_16,
     .format_str = "DEPTH_16",

cogl/cogl/cogl-pixel-format.h

@@ -101,9 +101,8 @@ G_BEGIN_DECLS
  * 4-6   = 2 bpp, not aligned (e.g. 565, 4444, 5551)
  * 7     = YUV: undefined bpp, undefined alignment
  * 9     = 2 bpp, aligned
- * 10    = depth, aligned (8, 16, 24, 32, 32f)
  * 11    = 8 bpp fp16
- * 12    = 3 bpp, not aligned
+ * 12    = 16 bpp fp32
  * 13    = 4 bpp, not aligned (e.g. 2101010)
  * 14    = 2 bpp, aligned (e.g. G_16)
  * 15    = 4 bpp, aligned (e.g. RG_1616)
@@ -186,6 +185,8 @@ G_BEGIN_DECLS
  * @COGL_PIXEL_FORMAT_BGRA_FP_16161616_PRE: Premultiplied BGRA half floating point, 64 bit
  * @COGL_PIXEL_FORMAT_ARGB_FP_16161616_PRE: Premultiplied ARGB half floating point, 64 bit
  * @COGL_PIXEL_FORMAT_ABGR_FP_16161616_PRE: Premultiplied ABGR half floating point, 64 bit
+ * @COGL_PIXEL_FORMAT_RGBA_FP_32323232: RGBA floating point, 128 bit
+ * @COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE: Premultiplied RGBA floating point, 128 bit
  *
  * Pixel formats used by Cogl. For the formats with a byte per
  * component, the order of the components specify the order in
@@ -266,6 +267,9 @@ typedef enum /*< prefix=COGL_PIXEL_FORMAT >*/
   COGL_PIXEL_FORMAT_ARGB_FP_16161616_PRE = (11 | COGL_A_BIT | COGL_PREMULT_BIT | COGL_AFIRST_BIT),
   COGL_PIXEL_FORMAT_ABGR_FP_16161616_PRE = (11 | COGL_A_BIT | COGL_PREMULT_BIT | COGL_BGR_BIT | COGL_AFIRST_BIT),
 
+  COGL_PIXEL_FORMAT_RGBA_FP_32323232 = (12 | COGL_A_BIT),
+  COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE = (12 | COGL_A_BIT | COGL_PREMULT_BIT),
+
   COGL_PIXEL_FORMAT_DEPTH_16  = (9 | COGL_DEPTH_BIT),
 
   COGL_PIXEL_FORMAT_DEPTH_24_STENCIL_8 = (3 | COGL_DEPTH_BIT | COGL_STENCIL_BIT)

cogl/cogl/driver/gl/gl/cogl-driver-gl.c

@@ -302,6 +302,13 @@ _cogl_driver_pixel_format_to_gl (CoglContext     *context,
                                          &gltype);
       break;
 
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232:
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE:
+      glintformat = GL_RGBA32F;
+      glformat = GL_RGBA;
+      gltype = GL_FLOAT;
+      break;
+
     case COGL_PIXEL_FORMAT_DEPTH_16:
       glintformat = GL_DEPTH_COMPONENT16;
       glformat = GL_DEPTH_COMPONENT;

cogl/cogl/driver/gl/gl/cogl-texture-driver-gl.c

@@ -438,6 +438,8 @@ _cogl_texture_driver_upload_supported (CoglContext *ctx,
     case COGL_PIXEL_FORMAT_RGBX_FP_16161616:
     case COGL_PIXEL_FORMAT_RGBA_FP_16161616:
     case COGL_PIXEL_FORMAT_RGBA_FP_16161616_PRE:
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232:
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE:
       return TRUE;
     case COGL_PIXEL_FORMAT_R_16:
     case COGL_PIXEL_FORMAT_RG_1616:

cogl/cogl/driver/gl/gles/cogl-driver-gles.c

@@ -68,6 +68,9 @@
 #ifndef GL_RGBA16F
 #define GL_RGBA16F 0x881A
 #endif
+#ifndef GL_RGBA32F
+#define GL_RGBA32F 0x8814
+#endif
 #ifndef GL_HALF_FLOAT
 #define GL_HALF_FLOAT 0x140B
 #endif
@@ -322,6 +325,20 @@ _cogl_driver_pixel_format_to_gl (CoglContext     *context,
                                          &gltype);
       break;
 
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232:
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE:
+      if (cogl_has_feature (context, COGL_FEATURE_ID_TEXTURE_HALF_FLOAT))
+        {
+          glintformat = GL_RGBA32F;
+          glformat = GL_RGBA;
+          gltype = GL_FLOAT;
+        }
+      else
+        {
+          g_assert_not_reached ();
+        }
+      break;
+
     case COGL_PIXEL_FORMAT_DEPTH_16:
       glintformat = GL_DEPTH_COMPONENT;
       glformat = GL_DEPTH_COMPONENT;
@@ -429,7 +446,11 @@ _cogl_driver_get_read_pixels_format (CoglContext     *context,
     case COGL_PIXEL_FORMAT_BGRA_FP_16161616_PRE:
     case COGL_PIXEL_FORMAT_ARGB_FP_16161616_PRE:
     case COGL_PIXEL_FORMAT_ABGR_FP_16161616_PRE:
-      g_assert_not_reached ();
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232:
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE:
+      required_gl_format = GL_RGBA;
+      required_gl_type = GL_FLOAT;
+      required_format = COGL_PIXEL_FORMAT_RGBA_FP_32323232;
       break;
 
     case COGL_PIXEL_FORMAT_DEPTH_16:
@@ -617,7 +638,8 @@ _cogl_driver_update_features (CoglContext *context,
 #endif
 
   if (COGL_CHECK_GL_VERSION (gl_major, gl_minor, 3, 2) ||
-      (_cogl_check_extension ("GL_OES_texture_half_float", gl_extensions) &&
+      (COGL_CHECK_GL_VERSION (gl_major, gl_minor, 3, 0) &&
+       _cogl_check_extension ("GL_OES_texture_half_float", gl_extensions) &&
        _cogl_check_extension ("GL_EXT_color_buffer_half_float", gl_extensions)))
     COGL_FLAGS_SET (context->features,
                     COGL_FEATURE_ID_TEXTURE_HALF_FLOAT, TRUE);

cogl/cogl/driver/gl/gles/cogl-texture-driver-gles.c

@@ -499,6 +499,8 @@ _cogl_texture_driver_upload_supported (CoglContext *ctx,
     case COGL_PIXEL_FORMAT_RGBX_FP_16161616:
     case COGL_PIXEL_FORMAT_RGBA_FP_16161616:
     case COGL_PIXEL_FORMAT_RGBA_FP_16161616_PRE:
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232:
+    case COGL_PIXEL_FORMAT_RGBA_FP_32323232_PRE:
       if (cogl_has_feature (ctx, COGL_FEATURE_ID_TEXTURE_HALF_FLOAT))
         return TRUE;
       else