From e01311a565faf5289f27cc4e7e31b8bf31ba1fa3 Mon Sep 17 00:00:00 2001
From: Benjamin Otte <otte@redhat.com>
Date: Sun, 17 Sep 2023 08:00:38 +0200
Subject: [PATCH] gpu: Add support for cross-fades

---
 gsk/gpu/gskgpunodeprocessor.c | 45 +++++++++++++++++++++++++++++++++--
 gsk/gpu/gskgputypesprivate.h  |  2 ++
 gsk/gpu/shaders/enums.glsl    |  2 ++
 gsk/gpu/shaders/pattern.glsl  | 17 +++++++++++++
 4 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/gsk/gpu/gskgpunodeprocessor.c b/gsk/gpu/gskgpunodeprocessor.c
index 10c5bac147..4104b022df 100644
--- a/gsk/gpu/gskgpunodeprocessor.c
+++ b/gsk/gpu/gskgpunodeprocessor.c
@@ -1006,6 +1006,47 @@ gsk_gpu_node_processor_create_conic_gradient_pattern (GskGpuPatternWriter *self,
   return TRUE;
 }
 
+static gboolean
+gsk_gpu_node_processor_create_cross_fade_pattern (GskGpuPatternWriter *self,
+                                                  GskRenderNode       *node)
+{
+  GskRenderNode *start_child, *end_child;
+
+  start_child = gsk_cross_fade_node_get_start_child (node);
+  end_child = gsk_cross_fade_node_get_end_child (node);
+
+  if (!gsk_gpu_node_processor_create_node_pattern (self, start_child))
+    return FALSE;
+  if (!gsk_rect_contains_rect (&start_child->bounds, &node->bounds))
+    {
+      gsk_gpu_buffer_writer_append_uint (&self->writer, GSK_GPU_PATTERN_CLIP);
+      gsk_gpu_buffer_writer_append_rect (&self->writer, &start_child->bounds, &self->offset);
+    }
+
+  gsk_gpu_buffer_writer_append_uint (&self->writer, GSK_GPU_PATTERN_PUSH_COLOR);
+
+  if (!gsk_gpu_pattern_writer_push_stack (self))
+    return FALSE;
+
+  if (!gsk_gpu_node_processor_create_node_pattern (self, end_child))
+    {
+      gsk_gpu_pattern_writer_pop_stack (self);
+      return FALSE;
+    }
+  if (!gsk_rect_contains_rect (&end_child->bounds, &node->bounds))
+    {
+      gsk_gpu_buffer_writer_append_uint (&self->writer, GSK_GPU_PATTERN_CLIP);
+      gsk_gpu_buffer_writer_append_rect (&self->writer, &end_child->bounds, &self->offset);
+    }
+
+  gsk_gpu_buffer_writer_append_uint (&self->writer, GSK_GPU_PATTERN_POP_CROSS_FADE);
+  gsk_gpu_buffer_writer_append_float (&self->writer, gsk_cross_fade_node_get_progress (node));
+
+  gsk_gpu_pattern_writer_pop_stack (self);
+
+  return TRUE;
+}
+
 static void
 gsk_gpu_node_processor_add_glyph_node (GskGpuNodeProcessor *self,
                                        GskRenderNode       *node)
@@ -1377,8 +1418,8 @@ static const struct
   },
   [GSK_CROSS_FADE_NODE] = {
     0,
-    NULL,
-    NULL,
+    gsk_gpu_node_processor_add_node_as_pattern,
+    gsk_gpu_node_processor_create_cross_fade_pattern,
   },
   [GSK_TEXT_NODE] = {
     0,
diff --git a/gsk/gpu/gskgputypesprivate.h b/gsk/gpu/gskgputypesprivate.h
index adbc3df9a4..512003c80b 100644
--- a/gsk/gpu/gskgputypesprivate.h
+++ b/gsk/gpu/gskgputypesprivate.h
@@ -45,5 +45,7 @@ typedef enum {
   GSK_GPU_PATTERN_ROUNDED_CLIP,
   GSK_GPU_PATTERN_REPEAT_PUSH,
   GSK_GPU_PATTERN_POSITION_POP,
+  GSK_GPU_PATTERN_PUSH_COLOR,
+  GSK_GPU_PATTERN_POP_CROSS_FADE,
 } GskGpuPatternType;
 
diff --git a/gsk/gpu/shaders/enums.glsl b/gsk/gpu/shaders/enums.glsl
index 2a548dc7e2..7635baf63d 100644
--- a/gsk/gpu/shaders/enums.glsl
+++ b/gsk/gpu/shaders/enums.glsl
@@ -22,6 +22,8 @@
 #define GSK_GPU_PATTERN_ROUNDED_CLIP 12u
 #define GSK_GPU_PATTERN_REPEAT_PUSH 13u
 #define GSK_GPU_PATTERN_POSITION_POP 14u
+#define GSK_GPU_PATTERN_PUSH_COLOR 15u
+#define GSK_GPU_PATTERN_POP_CROSS_FADE 16u
 
 #define TOP 0u
 #define RIGHT 1u
diff --git a/gsk/gpu/shaders/pattern.glsl b/gsk/gpu/shaders/pattern.glsl
index 8729dfa890..3d84cee6d1 100644
--- a/gsk/gpu/shaders/pattern.glsl
+++ b/gsk/gpu/shaders/pattern.glsl
@@ -140,6 +140,16 @@ position_pop_pattern (inout uint reader,
   pos = stack_pop ().xy;
 }
 
+void
+cross_fade_pattern (inout uint reader,
+                    inout vec4 color)
+{
+  vec4 start = stack_pop ();
+  float progress = read_float (reader);
+
+  color = mix (start, color, progress);
+}
+
 vec4
 glyphs_pattern (inout uint reader,
                 vec2       pos)
@@ -294,6 +304,13 @@ pattern (uint reader,
         case GSK_GPU_PATTERN_POSITION_POP:
           position_pop_pattern (reader, pos);
           break;
+        case GSK_GPU_PATTERN_PUSH_COLOR:
+          stack_push (color);
+          color = vec4 (0.0);
+          break;
+        case GSK_GPU_PATTERN_POP_CROSS_FADE:
+          cross_fade_pattern (reader, color);
+          break;
       }
     }
 }