[gtk+/wip/matthiasc/text-node: 125/125] More work on text nodes

[Matthias Clasen <matthiasc src gnome org>]

commit 344bad9788a007c6d326d54bb23055bab4f15f5b
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Sep 1 16:58:42 2017 -0400

    More work on text nodes
    
    This commit takes several steps towards rendering text
    like we want to. We use cairo to create a mask surface.
    In draw(), we use it to paint individual glyphs with the
    text color, unless we are dealing with color glyphs,
    in which case we use the surface as source. The surface
    will eventually be replaced by a font atlas texture.
    
    This commit also simplifies the text node api to just
    have a single offset, which determines the left end of
    the text baseline, like all our other text drawing APIs.
    
    We temporarily drop text node serialization, since it
    will have to change anyway.

 gsk/gskrendernode.h     |    6 +-
 gsk/gskrendernodeimpl.c |  224 +++++++++++++++++++----------------------------
 gtk/gskpango.c          |    8 +--
 3 files changed, 93 insertions(+), 145 deletions(-)
---
diff --git a/gsk/gskrendernode.h b/gsk/gskrendernode.h
index 46f6094..3816e1c 100644
--- a/gsk/gskrendernode.h
+++ b/gsk/gskrendernode.h
@@ -178,10 +178,8 @@ GDK_AVAILABLE_IN_3_92
 GskRenderNode *         gsk_text_node_new                       (PangoFont        *font,
                                                                  PangoGlyphString *glyphs,
                                                                  const GdkRGBA    *color,
-                                                                 int               x_offset,
-                                                                 int               y_offset,
-                                                                 double            base_x,
-                                                                 double            base_y);
+                                                                 double            x,
+                                                                 double            y);
 
 GDK_AVAILABLE_IN_3_92
 GskRenderNode *         gsk_blur_node_new                       (GskRenderNode *child,
diff --git a/gsk/gskrendernodeimpl.c b/gsk/gskrendernodeimpl.c
index 6ddbb2b..4b91076 100644
--- a/gsk/gskrendernodeimpl.c
+++ b/gsk/gskrendernodeimpl.c
@@ -3811,14 +3811,15 @@ struct _GskTextNode
 {
   GskRenderNode render_node;
 
-  PangoFont *font;
-  gboolean has_color;
   PangoGlyphString *glyphs;
+  cairo_surface_t *surface;
+
+  gboolean has_color;
   GdkRGBA color;
-  int x_offset;
-  int y_offset;
-  double base_x;
-  double base_y;
+  double x;
+  double y;
+  double ink_rect_y;
+  double ink_rect_height;
 };
 
 static void
@@ -3826,22 +3827,8 @@ gsk_text_node_finalize (GskRenderNode *node)
 {
   GskTextNode *self = (GskTextNode *) node;
 
-  g_object_unref (self->font);
   pango_glyph_string_free (self->glyphs);
-}
-
-static gboolean
-_pango_cairo_font_install (PangoFont *font,
-                           cairo_t   *cr)
-{
-  cairo_scaled_font_t *scaled_font = pango_cairo_font_get_scaled_font ((PangoCairoFont *)font);
-
-  if (G_UNLIKELY (scaled_font == NULL || cairo_scaled_font_status (scaled_font) != CAIRO_STATUS_SUCCESS))
-    return FALSE;
-
-  cairo_set_scaled_font (cr, scaled_font);
-
-  return TRUE;
+  cairo_surface_destroy (self->surface);
 }
 
 #ifndef STACK_BUFFER_SIZE
@@ -3851,37 +3838,39 @@ _pango_cairo_font_install (PangoFont *font,
 #define STACK_ARRAY_LENGTH(T) (STACK_BUFFER_SIZE / sizeof(T))
 
 static void
-gsk_text_node_draw (GskRenderNode *node,
-                    cairo_t       *cr)
+render_text (cairo_t          *cr,
+             PangoGlyphString *glyphs,
+             PangoFont        *font,
+             double            x,
+             double            y)
 {
-  GskTextNode *self = (GskTextNode *) node;
   int i, count;
   int x_position = 0;
+  cairo_scaled_font_t *scaled_font;
   cairo_glyph_t *cairo_glyphs;
   cairo_glyph_t stack_glyphs[STACK_ARRAY_LENGTH (cairo_glyph_t)];
 
-  cairo_save (cr);
-
-  cairo_translate (cr, self->x_offset, self->y_offset);
+  scaled_font = pango_cairo_font_get_scaled_font ((PangoCairoFont *)font);
+  if (G_UNLIKELY (!scaled_font || cairo_scaled_font_status (scaled_font) != CAIRO_STATUS_SUCCESS))
+    return;
 
-  gdk_cairo_set_source_rgba (cr, &self->color);
-  if (!_pango_cairo_font_install (self->font, cr))
-    goto done;
+  cairo_set_scaled_font (cr, scaled_font);
+  cairo_set_source_rgba (cr, 0, 0, 0, 1);
 
-  if (self->glyphs->num_glyphs > (int) G_N_ELEMENTS (stack_glyphs))
-    cairo_glyphs = g_new (cairo_glyph_t, self->glyphs->num_glyphs);
+  if (glyphs->num_glyphs > (int) G_N_ELEMENTS (stack_glyphs))
+    cairo_glyphs = g_new (cairo_glyph_t, glyphs->num_glyphs);
   else
     cairo_glyphs = stack_glyphs;
 
   count = 0;
-  for (i = 0; i < self->glyphs->num_glyphs; i++)
+  for (i = 0; i < glyphs->num_glyphs; i++)
     {
-      PangoGlyphInfo *gi = &self->glyphs->glyphs[i];
+      PangoGlyphInfo *gi = &glyphs->glyphs[i];
 
       if (gi->glyph != PANGO_GLYPH_EMPTY)
         {
-          double cx = self->base_x + (double)(x_position + gi->geometry.x_offset) / PANGO_SCALE;
-          double cy = gi->geometry.y_offset == 0 ? self->base_y : self->base_y + 
(double)(gi->geometry.y_offset) / PANGO_SCALE;
+          double cx = x + (double)(x_position + gi->geometry.x_offset) / PANGO_SCALE;
+          double cy = y + (double)(gi->geometry.y_offset) / PANGO_SCALE;
 
           if (!(gi->glyph & PANGO_GLYPH_UNKNOWN_FLAG))
             {
@@ -3898,108 +3887,71 @@ gsk_text_node_draw (GskRenderNode *node,
 
   if (cairo_glyphs != stack_glyphs)
     g_free (cairo_glyphs);
-
-done:
-  cairo_restore (cr);
 }
 
-#define GSK_TEXT_NODE_VARIANT_TYPE "(sddddiidda(uiiii))"
-
-static GVariant *
-gsk_text_node_serialize (GskRenderNode *node)
+static void
+gsk_text_node_draw (GskRenderNode *node,
+                    cairo_t       *cr)
 {
   GskTextNode *self = (GskTextNode *) node;
-  GVariant *v;
-  GVariantBuilder builder;
   int i;
-  PangoFontDescription *desc;
-  char *s;
+  int x_position = 0;
+
+  cairo_save (cr);
+
+  cairo_translate (cr, self->x, self->y);
+
+  gdk_cairo_set_source_rgba (cr, &self->color);
 
-  desc = pango_font_describe (self->font);
-  s = pango_font_description_to_string (desc);
   for (i = 0; i < self->glyphs->num_glyphs; i++)
     {
-      PangoGlyphInfo *glyph = &self->glyphs->glyphs[i];
-      g_variant_builder_add (&builder, "(uiiii)",
-                             glyph->glyph,
-                             glyph->geometry.width,
-                             glyph->geometry.x_offset,
-                             glyph->geometry.y_offset,
-                             glyph->attr.is_cluster_start);
-    }
+      PangoGlyphInfo *gi = &self->glyphs->glyphs[i];
+
+      if (gi->glyph != PANGO_GLYPH_EMPTY)
+        {
+          double cx = (double)(x_position + gi->geometry.x_offset) / PANGO_SCALE;
+          double cy = (double)(gi->geometry.y_offset) / PANGO_SCALE;
 
-  g_variant_builder_init (&builder, G_VARIANT_TYPE ("a(uiiii)"));
-  v = g_variant_new (GSK_TEXT_NODE_VARIANT_TYPE,
-                     s,
-                     self->color.red,
-                     self->color.green,
-                     self->color.blue,
-                     self->color.alpha,
-                     self->x_offset,
-                     self->y_offset,
-                     self->base_x,
-                     self->base_y,
-                     &builder);
+          if (!(gi->glyph & PANGO_GLYPH_UNKNOWN_FLAG))
+            {
+              cairo_rectangle (cr, cx,
+                                   cy + self->ink_rect_y,
+                                   gi->geometry.width / PANGO_SCALE,
+                                   self->ink_rect_height);
+              cairo_clip (cr);
+
+              cairo_move_to (cr, cx, cy + self->ink_rect_y);
+              if (self->has_color)
+                {
+                  cairo_set_source_surface (cr, self->surface, 0, self->ink_rect_y);
+                  cairo_paint (cr);
+                }
+              else
+                {
+                  cairo_mask_surface (cr, self->surface, 0, self->ink_rect_y);
+                }
+              cairo_reset_clip (cr);
+            }
+        }
+      x_position += gi->geometry.width;
+    }
 
-  g_free (s);
-  pango_font_description_free (desc);
+  cairo_restore (cr);
+}
 
-  return v;
+static GVariant *
+gsk_text_node_serialize (GskRenderNode *node)
+{
+  g_assert_not_reached ();
+  return NULL;
 }
 
 static GskRenderNode *
 gsk_text_node_deserialize (GVariant  *variant,
                            GError   **error)
 {
-  PangoFont *font;
-  PangoGlyphString *glyphs;
-  GVariantIter iter;
-  GskRenderNode *result;
-  PangoGlyphInfo glyph;
-  PangoFontDescription *desc;
-  PangoFontMap *fontmap;
-  PangoContext *context;
-  int cluster_start;
-  char *s;
-  GdkRGBA color;
-  int x_offset, y_offset;
-  double base_x, base_y;
-  int i;
-
-  if (!check_variant_type (variant, GSK_TEXT_NODE_VARIANT_TYPE, error))
-    return NULL;
-
-  g_variant_get (variant, "(&sddddiidda(uiiii))",
-                 &color.red, &color.green, &color.blue, &color.alpha,
-                 &x_offset, &y_offset,
-                 &base_x, &base_y,
-                 &s, &iter);
-
-  desc = pango_font_description_from_string (s);
-  fontmap = pango_cairo_font_map_get_default ();
-  context = pango_font_map_create_context (fontmap);
-  font = pango_font_map_load_font (fontmap, context, desc);
-
-  glyphs = pango_glyph_string_new ();
-  pango_glyph_string_set_size (glyphs, g_variant_iter_n_children (&iter));
-  i = 0;
-  while (g_variant_iter_next (&iter, "(uiiii)", &glyph.glyph, &glyph.geometry.width, 
&glyph.geometry.x_offset, &glyph.geometry.y_offset, &cluster_start))
-    {
-      glyph.attr.is_cluster_start = cluster_start;
-      glyphs->glyphs[i] = glyph;
-      i++;
-    }
-
-  result = gsk_text_node_new (font, glyphs, &color, /* FIXME: Avoid copying glyphs */
-                              x_offset, y_offset,
-                              base_x, base_y);
-
-  pango_glyph_string_free (glyphs);
-  pango_font_description_free (desc);
-  g_object_unref (context);
-  g_object_unref (font);
-
-  return result;
+  g_assert_not_reached ();
+  return NULL;
 }
 
 static const GskRenderNodeClass GSK_TEXT_NODE_CLASS = {
@@ -4033,13 +3985,12 @@ GskRenderNode *
 gsk_text_node_new (PangoFont        *font,
                    PangoGlyphString *glyphs,
                    const GdkRGBA    *color,
-                   int               x_offset,
-                   int               y_offset,
-                   double            base_x,
-                   double            base_y)
+                   double            x,
+                   double            y)
 {
   GskTextNode *self;
   PangoRectangle ink_rect;
+  cairo_t *cr;
 
   pango_glyph_string_extents (glyphs, font, &ink_rect, NULL);
   pango_extents_to_pixels (&ink_rect, NULL);
@@ -4050,23 +4001,28 @@ gsk_text_node_new (PangoFont        *font,
 
   self = (GskTextNode *) gsk_render_node_new (&GSK_TEXT_NODE_CLASS, 0);
 
-  self->font = g_object_ref (font);
   self->glyphs = pango_glyph_string_copy (glyphs);
   self->color = *color;
-  self->x_offset = x_offset;
-  self->y_offset = y_offset;
-  self->base_x = base_x;
-  self->base_y = base_y;
+  self->x = x;
+  self->y = y;
+  self->ink_rect_y = ink_rect.y;
+  self->ink_rect_height = ink_rect.height;
 
   self->has_color = font_has_color_glyphs (font);
 
-
   graphene_rect_init (&self->render_node.bounds,
-                      x_offset + base_x + ink_rect.x,
-                      y_offset + base_y + ink_rect.y,
-                      ink_rect.width,
+                      x,
+                      y + ink_rect.y,
+                      ink_rect.x + ink_rect.width,
                       ink_rect.height);
 
+  self->surface = cairo_image_surface_create (self->has_color ? CAIRO_FORMAT_ARGB32 : CAIRO_FORMAT_A8,
+                                              ink_rect.x + ink_rect.width,
+                                              ink_rect.height);
+  cr = cairo_create (self->surface);
+  render_text (cr, glyphs, font, 0, - ink_rect.y);
+  cairo_destroy (cr);
+
   return &self->render_node;
 }
 
diff --git a/gtk/gskpango.c b/gtk/gskpango.c
index 698688a..ff91d08 100644
--- a/gtk/gskpango.c
+++ b/gtk/gskpango.c
@@ -112,8 +112,6 @@ gsk_pango_renderer_show_text_glyphs (PangoRenderer        *renderer,
                                      int                   y)
 {
   GskPangoRenderer *crenderer = (GskPangoRenderer *) (renderer);
-  double base_x = (double)x / PANGO_SCALE;
-  double base_y = (double)y / PANGO_SCALE;
   int x_offset, y_offset;
   GskRenderNode *node;
   GdkRGBA color;
@@ -121,7 +119,7 @@ gsk_pango_renderer_show_text_glyphs (PangoRenderer        *renderer,
   gtk_snapshot_get_offset (crenderer->snapshot, &x_offset, &y_offset);
   get_color (crenderer, PANGO_RENDER_PART_FOREGROUND, &color);
 
-  node = gsk_text_node_new (font, glyphs, &color, x_offset, y_offset, base_x, base_y);
+  node = gsk_text_node_new (font, glyphs, &color, x_offset + (double)x/PANGO_SCALE, y_offset + 
(double)y/PANGO_SCALE);
   if (node == NULL)
     return;
 
@@ -132,12 +130,8 @@ gsk_pango_renderer_show_text_glyphs (PangoRenderer        *renderer,
       gsk_render_node_set_name (node, name);
     }
 
-  gtk_snapshot_offset (crenderer->snapshot, base_x, base_y);
-
   gtk_snapshot_append_node (crenderer->snapshot, node);
   gsk_render_node_unref (node);
-
-  gtk_snapshot_offset (crenderer->snapshot, -base_x, -base_y);
 }
 
 static void