[gtk: 1/2] gl: Track the current uniform state for custom programs

[Matthias Clasen <matthiasc src gnome org>]

commit 51ab56d33aa158cac0a0cc03fa2828807729cda1
Author: Alexander Larsson <alexl redhat com>
Date:   Tue Sep 29 11:52:39 2020 +0200

    gl: Track the current uniform state for custom programs
    
    This allows us to avoid updating uniforms if that is not necessary. This
    in turn allows us to sometimes reuse the same draw op by just extending the
    vertex array size we draw rather than doing a separate glDraw call.
    
    For example, in the fishbowl demo, all the icons added at the same
    time will have the same time and size, so we emit single draw calls
    with 100s of triangles instead of 100s of draw calls with 2 triangles.

 gsk/gl/gskglrenderops.c        | 21 +++++++++++++++++++++
 gsk/gl/gskglrenderopsprivate.h |  6 ++++++
 2 files changed, 27 insertions(+)
---
diff --git a/gsk/gl/gskglrenderops.c b/gsk/gl/gskglrenderops.c
index 1fc9d02810..63273db93d 100644
--- a/gsk/gl/gskglrenderops.c
+++ b/gsk/gl/gskglrenderops.c
@@ -640,7 +640,28 @@ ops_set_gl_shader_args (RenderOpBuilder       *builder,
                         float                  height,
                         const guchar          *uniform_data)
 {
+  ProgramState *current_program_state = get_current_program_state (builder);
   OpGLShader *op;
+  gsize args_size = gsk_gl_shader_get_args_size (shader);
+
+  if (current_program_state)
+    {
+      if (current_program_state->gl_shader.width == width &&
+          current_program_state->gl_shader.height == height &&
+          current_program_state->gl_shader.uniform_data_len == args_size &&
+          memcmp (current_program_state->gl_shader.uniform_data, uniform_data, args_size) == 0)
+        return;
+
+      current_program_state->gl_shader.width = width;
+      current_program_state->gl_shader.height = height;
+      if (args_size > sizeof (current_program_state->gl_shader.uniform_data))
+        current_program_state->gl_shader.uniform_data_len = 0;
+      else
+        {
+          current_program_state->gl_shader.uniform_data_len = args_size;
+          memcpy (current_program_state->gl_shader.uniform_data, uniform_data, args_size);
+        }
+    }
 
   op = ops_begin (builder, OP_CHANGE_GL_SHADER_ARGS);
   op->shader = shader;
diff --git a/gsk/gl/gskglrenderopsprivate.h b/gsk/gl/gskglrenderopsprivate.h
index 38b5756a9c..6f90a0c212 100644
--- a/gsk/gl/gskglrenderopsprivate.h
+++ b/gsk/gl/gskglrenderopsprivate.h
@@ -79,6 +79,12 @@ typedef struct
       float end;
       float radius[2]; /* h/v */
     } radial_gradient;
+    struct {
+      float width;
+      float height;
+      gint uniform_data_len;
+      guchar uniform_data[32];
+    } gl_shader;
   };
 } ProgramState;