[gtk/wip/baedert/for-master: 7/7] gl shaders: unify frag coord handling

[Timm Bäder <baedert src gnome org>]

commit 52ae384bfdfa17c7211dbc103287d4fd580e790f
Author: Timm Bäder <mail baedert org>
Date:   Sun May 10 09:20:53 2020 +0200

    gl shaders: unify frag coord handling

 gsk/resources/glsl/border.glsl                  |  8 +++-----
 gsk/resources/glsl/inset_shadow.glsl            |  9 +++------
 gsk/resources/glsl/linear_gradient.glsl         | 10 +---------
 gsk/resources/glsl/outset_shadow.glsl           |  7 ++-----
 gsk/resources/glsl/preamble.fs.glsl             | 25 +++++++++++++++++++------
 gsk/resources/glsl/unblurred_outset_shadow.glsl |  9 +++------
 6 files changed, 31 insertions(+), 37 deletions(-)
---
diff --git a/gsk/resources/glsl/border.glsl b/gsk/resources/glsl/border.glsl
index 812d365431..894843cc50 100644
--- a/gsk/resources/glsl/border.glsl
+++ b/gsk/resources/glsl/border.glsl
@@ -32,12 +32,10 @@ _IN_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
 _IN_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
-  vec4 f = gl_FragCoord;
-  f.x += u_viewport.x;
-  f.y = (u_viewport.y + u_viewport.w) - f.y;
+  vec2 frag = get_frag_coord();
 
-  float alpha = clamp(rounded_rect_coverage(decode_rect(transformed_outside_outline), f.xy) -
-                      rounded_rect_coverage(decode_rect(transformed_inside_outline), f.xy),
+  float alpha = clamp(rounded_rect_coverage(decode_rect(transformed_outside_outline), frag) -
+                      rounded_rect_coverage(decode_rect(transformed_inside_outline), frag),
                       0.0, 1.0);
 
   setOutputColor(final_color * alpha);
diff --git a/gsk/resources/glsl/inset_shadow.glsl b/gsk/resources/glsl/inset_shadow.glsl
index b3ba05a41f..238540c731 100644
--- a/gsk/resources/glsl/inset_shadow.glsl
+++ b/gsk/resources/glsl/inset_shadow.glsl
@@ -33,13 +33,10 @@ _IN_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
 _IN_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
-  vec4 f = gl_FragCoord;
+  vec2 frag = get_frag_coord();
 
-  f.x += u_viewport.x;
-  f.y = (u_viewport.y + u_viewport.w) - f.y;
-
-  float alpha = clamp (rounded_rect_coverage(decode_rect(transformed_outside_outline), f.xy) -
-                       rounded_rect_coverage(decode_rect(transformed_inside_outline), f.xy),
+  float alpha = clamp (rounded_rect_coverage(decode_rect(transformed_outside_outline), frag) -
+                       rounded_rect_coverage(decode_rect(transformed_inside_outline), frag),
                        0.0, 1.0);
 
   setOutputColor(final_color * alpha);
diff --git a/gsk/resources/glsl/linear_gradient.glsl b/gsk/resources/glsl/linear_gradient.glsl
index 6814eed53f..cffe39294d 100644
--- a/gsk/resources/glsl/linear_gradient.glsl
+++ b/gsk/resources/glsl/linear_gradient.glsl
@@ -47,17 +47,9 @@ _IN_ float gradientLength;
 _IN_ vec4 color_stops[8];
 _IN_ float color_offsets[8];
 
-
-vec4 fragCoord() {
-  vec4 f = gl_FragCoord;
-  f.x += u_viewport.x;
-  f.y = (u_viewport.y + u_viewport.w) - f.y;
-  return f;
-}
-
 void main() {
   // Position relative to startPoint
-  vec2 pos = fragCoord().xy - startPoint;
+  vec2 pos = get_frag_coord() - startPoint;
 
   // Current pixel, projected onto the line between the start point and the end point
   // The projection will be relative to the start point!
diff --git a/gsk/resources/glsl/outset_shadow.glsl b/gsk/resources/glsl/outset_shadow.glsl
index 4111ddcea8..40ef45f648 100644
--- a/gsk/resources/glsl/outset_shadow.glsl
+++ b/gsk/resources/glsl/outset_shadow.glsl
@@ -25,13 +25,10 @@ _IN_ vec4 final_color;
 _IN_ _ROUNDED_RECT_UNIFORM_ transformed_outline;
 
 void main() {
-  vec4 f = gl_FragCoord;
-
-  f.x += u_viewport.x;
-  f.y = (u_viewport.y + u_viewport.w) - f.y;
+  vec2 frag = get_frag_coord();
 
   float alpha = Texture(u_source, vUv).a;
-  alpha *= (1.0 -  clamp(rounded_rect_coverage(decode_rect(transformed_outline), f.xy), 0.0, 1.0));
+  alpha *= (1.0 -  clamp(rounded_rect_coverage(decode_rect(transformed_outline), frag), 0.0, 1.0));
 
   vec4 color = final_color * alpha;
 
diff --git a/gsk/resources/glsl/preamble.fs.glsl b/gsk/resources/glsl/preamble.fs.glsl
index 5107470e00..cadbaf1331 100644
--- a/gsk/resources/glsl/preamble.fs.glsl
+++ b/gsk/resources/glsl/preamble.fs.glsl
@@ -84,19 +84,32 @@ vec4 Texture(sampler2D sampler, vec2 texCoords) {
 #endif
 }
 
-void setOutputColor(vec4 color) {
-  vec4 f = gl_FragCoord;
+#ifdef GSK_GL3
+layout(origin_upper_left) in vec4 gl_FragCoord;
+#endif
+
+vec2 get_frag_coord() {
+  vec2 fc = gl_FragCoord.xy;
+
+#ifdef GSK_GL3
+  fc += u_viewport.xy;
+#else
+  fc.x += u_viewport.x;
+  fc.y = (u_viewport.y + u_viewport.w) - fc.y;
+#endif
 
-  f.x += u_viewport.x;
-  f.y = (u_viewport.y + u_viewport.w) - f.y;
+  return fc;
+}
 
+void setOutputColor(vec4 color) {
+  vec2 f = get_frag_coord();
 
   // We do *NOT* transform the clip rect here since we already
   // need to do that on the CPU.
 #if defined(GSK_GLES) || defined(GSK_LEGACY)
-  gl_FragColor = color * rounded_rect_coverage(create_rect(u_clip_rect), f.xy);
+  gl_FragColor = color * rounded_rect_coverage(create_rect(u_clip_rect), f);
 #else
-  outputColor = color * rounded_rect_coverage(create_rect(u_clip_rect), f.xy);
+  outputColor = color * rounded_rect_coverage(create_rect(u_clip_rect), f);
 #endif
   /*outputColor = color;*/
 }
diff --git a/gsk/resources/glsl/unblurred_outset_shadow.glsl b/gsk/resources/glsl/unblurred_outset_shadow.glsl
index 77c02be8e1..419605e092 100644
--- a/gsk/resources/glsl/unblurred_outset_shadow.glsl
+++ b/gsk/resources/glsl/unblurred_outset_shadow.glsl
@@ -33,13 +33,10 @@ _IN_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
 _IN_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
-  vec4 f = gl_FragCoord;
+  vec2 frag = get_frag_coord();
 
-  f.x += u_viewport.x;
-  f.y = (u_viewport.y + u_viewport.w) - f.y;
-
-  float alpha = clamp(rounded_rect_coverage(decode_rect(transformed_outside_outline), f.xy) -
-                      rounded_rect_coverage(decode_rect(transformed_inside_outline), f.xy),
+  float alpha = clamp(rounded_rect_coverage(decode_rect(transformed_outside_outline), frag) -
+                      rounded_rect_coverage(decode_rect(transformed_inside_outline), frag),
                       0.0, 1.0);
 
   setOutputColor(final_color * alpha);