From 91d970e9c5f612f62118ac88188959e57e048d54 Mon Sep 17 00:00:00 2001
From: Benjamin Otte <otte@redhat.com>
Date: Wed, 3 Jul 2024 07:45:48 +0200
Subject: [PATCH] gpu: Add shaders for the new specialization constant

This adds the following functions:

output_color_from_alt()
alt_color_from_output()
  Converts between the two colors

output_color_alpha()
alt_color_alpha()
  Multiplies a color with an alpha value
---
 gsk/gpu/shaders/color.glsl         | 127 +++++++++++++++++++++++++++++
 gsk/gpu/shaders/gskgpuconvert.glsl |  18 ----
 2 files changed, 127 insertions(+), 18 deletions(-)

diff --git a/gsk/gpu/shaders/color.glsl b/gsk/gpu/shaders/color.glsl
index 3f18784593..91538b2419 100644
--- a/gsk/gpu/shaders/color.glsl
+++ b/gsk/gpu/shaders/color.glsl
@@ -1,6 +1,17 @@
 #ifndef _COLOR_
 #define _COLOR_
 
+#define COLOR_SPACE_OUTPUT_PREMULTIPLIED (1u << 2)
+#define COLOR_SPACE_ALT_PREMULTIPLIED    (1u << 3)
+#define COLOR_SPACE_OUTPUT_SHIFT 8u
+#define COLOR_SPACE_ALT_SHIFT 16u
+#define COLOR_SPACE_COLOR_STATE_MASK 0xFFu
+
+#define OUTPUT_COLOR_SPACE ((GSK_COLOR_STATES >> COLOR_SPACE_OUTPUT_SHIFT) & COLOR_SPACE_COLOR_STATE_MASK)
+#define ALT_COLOR_SPACE ((GSK_COLOR_STATES >> COLOR_SPACE_ALT_SHIFT) & COLOR_SPACE_COLOR_STATE_MASK)
+#define OUTPUT_PREMULTIPLIED ((GSK_COLOR_STATES & COLOR_SPACE_OUTPUT_PREMULTIPLIED) == COLOR_SPACE_OUTPUT_PREMULTIPLIED)
+#define ALT_PREMULTIPLIED ((GSK_COLOR_STATES & COLOR_SPACE_ALT_PREMULTIPLIED) == COLOR_SPACE_ALT_PREMULTIPLIED)
+
 vec4
 color_premultiply (vec4 color)
 {
@@ -13,6 +24,122 @@ color_unpremultiply (vec4 color)
   return color.a > 0.0 ? color / vec4 (color.aaa, 1.0) : color;
 }
 
+float
+srgb_eotf (float v)
+{
+  if (v >= 0.04045)
+    return pow (((v + 0.055) / (1.0 + 0.055)), 2.4);
+  else
+    return v / 12.92;
+}
+
+float
+srgb_oetf (float v)
+{
+  if (v > 0.0031308)
+    return 1.055 * pow (v, 1.0 / 2.4) - 0.055;
+  else
+    return 12.92 * v;
+}
+
+vec4
+alt_color_alpha (vec4  color,
+                 float alpha)
+{
+  if (ALT_PREMULTIPLIED)
+    return color * alpha;
+  else
+    return vec4 (color.rgb, color.a * alpha);
+}
+
+vec4
+output_color_alpha (vec4  color,
+                    float alpha)
+{
+  if (OUTPUT_PREMULTIPLIED)
+    return color * alpha;
+  else
+    return vec4 (color.rgb, color.a * alpha);
+}
+
+vec4
+alt_color_from_output (vec4 color)
+{
+  if (OUTPUT_COLOR_SPACE == ALT_COLOR_SPACE)
+    {
+      if (OUTPUT_PREMULTIPLIED && !ALT_PREMULTIPLIED)
+        return color_unpremultiply (color);
+      else if (!OUTPUT_PREMULTIPLIED && ALT_PREMULTIPLIED)
+        return color_premultiply (color);
+      else
+        return color;
+    }
+
+  if (OUTPUT_PREMULTIPLIED)
+    color = color_unpremultiply (color);
+
+  if (OUTPUT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB &&
+      ALT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB_LINEAR)
+    {
+      color = vec4 (srgb_eotf (color.r),
+                    srgb_eotf (color.g),
+                    srgb_eotf (color.b),
+                    color.a);
+    }
+  else if (OUTPUT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB_LINEAR &&
+           ALT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB)
+    {
+      color = vec4 (srgb_oetf (color.r),
+                    srgb_oetf (color.g),
+                    srgb_oetf (color.b),
+                    color.a);
+    }
+
+  if (ALT_PREMULTIPLIED)
+    color = color_premultiply (color);
+
+  return color;
+}
+
+vec4
+output_color_from_alt (vec4 color)
+{
+  if (OUTPUT_COLOR_SPACE == ALT_COLOR_SPACE)
+    {
+      if (ALT_PREMULTIPLIED && !OUTPUT_PREMULTIPLIED)
+        return color_unpremultiply (color);
+      else if (!ALT_PREMULTIPLIED && OUTPUT_PREMULTIPLIED)
+        return color_premultiply (color);
+      else
+        return color;
+    }
+
+  if (ALT_PREMULTIPLIED)
+    color = color_unpremultiply (color);
+
+  if (ALT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB &&
+      OUTPUT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB_LINEAR)
+    {
+      color = vec4 (srgb_eotf (color.r),
+                    srgb_eotf (color.g),
+                    srgb_eotf (color.b),
+                    color.a);
+    }
+  else if (ALT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB_LINEAR &&
+           OUTPUT_COLOR_SPACE == GDK_COLOR_STATE_ID_SRGB)
+    {
+      color = vec4 (srgb_oetf (color.r),
+                    srgb_oetf (color.g),
+                    srgb_oetf (color.b),
+                    color.a);
+    }
+
+  if (OUTPUT_PREMULTIPLIED)
+    color = color_premultiply (color);
+
+  return color;
+}
+
 float
 luminance (vec3 color)
 {
diff --git a/gsk/gpu/shaders/gskgpuconvert.glsl b/gsk/gpu/shaders/gskgpuconvert.glsl
index f6e6c57d96..04dcbe8f61 100644
--- a/gsk/gpu/shaders/gskgpuconvert.glsl
+++ b/gsk/gpu/shaders/gskgpuconvert.glsl
@@ -13,24 +13,6 @@
 #define SOURCE_COLOR_STATE ((GSK_VARIATION >> VARIATION_SOURCE_SHIFT) & VARIATION_COLOR_STATE_MASK)
 #define TARGET_COLOR_STATE ((GSK_VARIATION >> VARIATION_TARGET_SHIFT) & VARIATION_COLOR_STATE_MASK)
 
-float
-srgb_eotf (float v)
-{
-  if (v >= 0.04045)
-    return pow (((v + 0.055) / (1.0 + 0.055)), 2.4);
-  else
-    return v / 12.92;
-}
-
-float
-srgb_oetf (float v)
-{
-  if (v > 0.0031308)
-    return 1.055 * pow (v, 1.0 / 2.4) - 0.055;
-  else
-    return 12.92 * v;
-}
-
 vec4
 srgb_to_linear_srgb (vec4 color)
 {