[gtk/wip/baedert/transforms6: 3/31] gl renderer: Expand matrix metadata extraction

[Timm Bäder <baedert src gnome org>]

commit 12378f0afa8c0784c697d6120e51b93e99b0c60e
Author: Timm Bäder <tbaeder redhat com>
Date:   Wed Nov 28 09:30:27 2018 +0100

    gl renderer: Expand matrix metadata extraction
    
    Instead of getting the translation x/y everytime we use the modelview,
    get it once, when extracting the metadata. Do the same with the scale.
    And save if the matrix is "simple" at all, i.e. if it only consists of a
    translation and/or scale. This will be helpful later when we start
    drawing transformed nodes on textures.

 gsk/gl/gskglrenderops.c        | 86 ++++++++++++++++++++----------------------
 gsk/gl/gskglrenderopsprivate.h |  9 ++++-
 2 files changed, 47 insertions(+), 48 deletions(-)
---
diff --git a/gsk/gl/gskglrenderops.c b/gsk/gl/gskglrenderops.c
index f0ef2f633e..1ac8f8866e 100644
--- a/gsk/gl/gskglrenderops.c
+++ b/gsk/gl/gskglrenderops.c
@@ -7,7 +7,6 @@ ops_finish (RenderOpBuilder *builder)
     g_array_free (builder->mv_stack, TRUE);
 }
 
-
 static inline void
 rgba_to_float (const GdkRGBA *c,
                float         *f)
@@ -28,38 +27,9 @@ ops_get_scale (const RenderOpBuilder *builder)
 
   head = &g_array_index (builder->mv_stack, MatrixStackEntry, builder->mv_stack->len - 1);
 
-  return head->metadata.scale;
-}
-
-static inline gboolean
-matrix_is_only_translation (const graphene_matrix_t *mat)
-{
-  graphene_vec4_t row1;
-  graphene_vec4_t row2;
-  graphene_vec4_t row3;
-  graphene_vec4_t row;
-
-  graphene_vec4_init (&row1, 1, 0, 0, 0);
-  graphene_vec4_init (&row2, 0, 1, 0, 0);
-  graphene_vec4_init (&row3, 0, 0, 1, 0);
-
-  graphene_matrix_get_row (mat, 0, &row);
-  if (!graphene_vec4_equal (&row1, &row))
-    return FALSE;
-
-  graphene_matrix_get_row (mat, 1, &row);
-  if (!graphene_vec4_equal (&row2, &row))
-    return FALSE;
-
-  graphene_matrix_get_row (mat, 2, &row);
-  if (!graphene_vec4_equal (&row3, &row))
-    return FALSE;
-
-  graphene_matrix_get_row (mat, 3, &row);
-  if (graphene_vec4_get_w (&row) != 1)
-    return FALSE;
-
-  return TRUE;
+  /* TODO: Use two separate values */
+  return MAX (head->metadata.scale_x,
+              head->metadata.scale_y);
 }
 
 static void
@@ -69,10 +39,9 @@ extract_matrix_metadata (const graphene_matrix_t *m,
   graphene_vec3_t col1;
   graphene_vec3_t col2;
 
-  /* Is this matrix JUST a translation? */
-  md->is_only_translation = matrix_is_only_translation (m);
-
-  /* TODO: We should probably split this up into two values... */
+  /* Translate */
+  md->translate_x = graphene_matrix_get_value (m, 3, 0);
+  md->translate_y = graphene_matrix_get_value (m, 3, 1);
 
   /* Scale */
   graphene_vec3_init (&col1,
@@ -85,9 +54,36 @@ extract_matrix_metadata (const graphene_matrix_t *m,
                       graphene_matrix_get_value (m, 1, 1),
                       graphene_matrix_get_value (m, 2, 1));
 
-  md->scale = MAX (graphene_vec3_length (&col1),
-                   graphene_vec3_length (&col2));
-
+  md->scale_x = graphene_vec3_length (&col1);
+  md->scale_y = graphene_vec3_length (&col2);
+
+  /* A simple matrix (in our case) is one that doesn't do anything but scale
+   * and/or translate.
+   *
+   * For orher matrices, we fall back to offscreen drawing.
+   */
+  md->simple = TRUE;
+  {
+    static const guchar check_zero[4][4] = {
+      { 0, 1, 0, 1 },        /* If any of the values marked as '1' here is non-zero, */
+      { 1, 0, 0, 1 },        /* We have to resort to offscreen drawing later on. */
+      { 1, 1, 0, 1 },
+      { 0, 0, 0, 0 },
+    };
+    int x, y;
+
+    for (x = 0; x < 4; x ++)
+      for (y = 0; y < 4; y ++)
+          if (check_zero[y][x] &&
+              graphene_matrix_get_value (m, y, x) != 0.0f)
+            {
+              md->simple = FALSE;
+              goto out;
+            }
+  }
+
+out:
+  md->only_translation = (md->simple && md->scale_x == 0 && md->scale_y == 0);
 }
 
 
@@ -103,14 +99,12 @@ ops_transform_bounds_modelview (const RenderOpBuilder *builder,
 
   head = &g_array_index (builder->mv_stack, MatrixStackEntry, builder->mv_stack->len - 1);
 
-  if (head->metadata.is_only_translation)
+  if (head->metadata.only_translation)
     {
-      graphene_vec4_t row4;
-
-      /* TODO: We could do the get_row here only once, when setting the new modelview matrix. */
-      graphene_matrix_get_row (builder->current_modelview, 3, &row4);
       *dst = *src;
-      graphene_rect_offset (dst, graphene_vec4_get_x (&row4), graphene_vec4_get_y (&row4));
+      graphene_rect_offset (dst,
+                            head->metadata.translate_x,
+                            head->metadata.translate_y);
     }
   else
     {
diff --git a/gsk/gl/gskglrenderopsprivate.h b/gsk/gl/gskglrenderopsprivate.h
index 18a4734257..7b0b1f824f 100644
--- a/gsk/gl/gskglrenderopsprivate.h
+++ b/gsk/gl/gskglrenderopsprivate.h
@@ -16,8 +16,13 @@
 
 typedef struct
 {
-  guint is_only_translation : 1;
-  float scale;
+  float translate_x;
+  float translate_y;
+  float scale_x;
+  float scale_y;
+
+  guint simple : 1;
+  guint only_translation : 1;
 } OpsMatrixMetadata;
 
 typedef struct