[Gimp-developer] [PATCH] app: Use SHM transport for data transfer for display

[Chris Wilson <chris chris-wilson co uk>]

Recent Cairo uses SHM transports when available, and exposes the ability
for its users to manage images shared between it and the display.
This allows us to eliminate copies, and if the architecture supports it
even to upload directly into GPU addressable memory without any copies
(all in normal system memory so we suffer no performance penalty when
applying the filters). The caveat is that we need to be aware of the
synchronize requirements, the cairo_surface_flush and
cairo_surface_mark_dirty, around access to the transport image. To
reduce the frequency of these barriers, we can subdivide the transport
image into small chunks as to satisfy individual updates and delay the
synchronisation barrier until we are forced to reuse earlier pixels.

Note this bumps the required Cairo version to 1.12, and please be aware
that the XSHM transport requires bug fixes from cairo.git (will be
1.12.12)

Cc: Michael Natterer <mitch gimp org>
---
 app/display/gimpdisplayshell-callbacks.c |    3 +
 app/display/gimpdisplayshell-render.c    |  223 +++++++++++++++++++++++++++---
 app/display/gimpdisplayshell-render.h    |    3 +
 app/display/gimpdisplayshell.c           |   16 +--
 app/display/gimpdisplayshell.h           |    7 +
 configure.ac                             |    2 +-
 6 files changed, 220 insertions(+), 34 deletions(-)

diff --git a/app/display/gimpdisplayshell-callbacks.c b/app/display/gimpdisplayshell-callbacks.c
index e8cf44d..4aa25f7 100644
--- a/app/display/gimpdisplayshell-callbacks.c
+++ b/app/display/gimpdisplayshell-callbacks.c
@@ -38,6 +38,7 @@
 #include "gimpdisplayshell-appearance.h"
 #include "gimpdisplayshell-callbacks.h"
 #include "gimpdisplayshell-draw.h"
+#include "gimpdisplayshell-render.h"
 #include "gimpdisplayshell-scroll.h"
 #include "gimpdisplayshell-selection.h"
 #include "gimpdisplayshell-title.h"
@@ -109,6 +110,8 @@ gimp_display_shell_canvas_realize (GtkWidget        *canvas,
 
   /*  allow shrinking  */
   gtk_widget_set_size_request (GTK_WIDGET (shell), 0, 0);
+
+  gimp_display_shell_xfer_realize (shell);
 }
 
 void
diff --git a/app/display/gimpdisplayshell-render.c b/app/display/gimpdisplayshell-render.c
index 67d1c50..38eec27 100644
--- a/app/display/gimpdisplayshell-render.c
+++ b/app/display/gimpdisplayshell-render.c
@@ -42,6 +42,199 @@
 #include "gimpdisplayshell-render.h"
 #include "gimpdisplayshell-scroll.h"
 
+static struct rtree_node *
+rtree_node_create (struct rtree *rtree, struct rtree_node **prev,
+		   int x, int y, int w, int h)
+{
+    struct rtree_node *node;
+
+    node = g_slice_alloc (sizeof (*node));
+    if (node == NULL)
+	return NULL;
+
+    node->children[0] = NULL;
+    node->x = x;
+    node->y = y;
+    node->w = w;
+    node->h = h;
+
+    node->next = *prev;
+    *prev = node;
+
+    return node;
+}
+
+static void
+rtree_node_destroy (struct rtree *rtree, struct rtree_node *node)
+{
+    int i;
+
+    for (i = 0; i < 4 && node->children[i] != NULL; i++)
+	rtree_node_destroy (rtree, node->children[i]);
+
+    g_slice_free (struct rtree_node, node);
+}
+
+static struct rtree_node *
+rtree_node_insert (struct rtree *rtree, struct rtree_node **prev,
+		   struct rtree_node *node, int w, int h)
+{
+    *prev = node->next;
+
+    if (((node->w - w) | (node->h - h)) > 1) {
+	int ww = node->w - w;
+	int hh = node->h - h;
+	int i = 0;
+
+	node->children[i] = rtree_node_create (rtree, prev,
+					       node->x, node->y,
+					       w, h);
+	if (node->children[i] == NULL)
+	    return node;
+	i++;
+
+	if (ww > 1) {
+	    node->children[i] = rtree_node_create (rtree, prev,
+						   node->x + w, node->y,
+						   ww, h);
+	    if (node->children[i])
+		i++;
+	}
+
+	if (hh > 1) {
+	    node->children[i] = rtree_node_create (rtree, prev,
+						   node->x, node->y + h,
+						   ww, hh);
+	    if (node->children[i])
+		i++;
+
+	    if (w > 1) {
+		node->children[i] = rtree_node_create (rtree, prev,
+						       node->x + w,
+						       node->y + h,
+						       ww, hh);
+		if (node->children[i])
+		    i++;
+	    }
+	}
+
+	if (i < 4)
+	    node->children[i] = NULL;
+
+	node = node->children[0];
+    }
+
+    return node;
+}
+
+static struct rtree_node *
+rtree_insert (struct rtree *rtree, int w, int h)
+{
+    struct rtree_node *node, **prev;
+
+    for (prev = &rtree->available; (node = *prev); prev = &node->next)
+	if (node->w >= w && w < 2 * node->w && node->h >= h && h < 2 * node->h)
+	    return rtree_node_insert (rtree, prev, node, w, h);
+
+    for (prev = &rtree->available; (node = *prev); prev = &node->next)
+	if (node->w >= w && node->h >= h)
+	    return rtree_node_insert (rtree, prev, node, w, h);
+
+    return NULL;
+}
+
+static void
+rtree_init (struct rtree *rtree, int w, int h)
+{
+    rtree->root.w = w;
+    rtree->root.h = h;
+    rtree->root.children[0] = NULL;
+    rtree->root.next = NULL;
+    rtree->available = &rtree->root;
+}
+
+static void
+rtree_reset (struct rtree *rtree)
+{
+    int i;
+
+    for (i = 0; i < 4 && rtree->root.children[i] != NULL; i++)
+	rtree_node_destroy (rtree, rtree->root.children[i]);
+    rtree->root.children[0] = NULL;
+
+    rtree->root.next = NULL;
+    rtree->available = &rtree->root;
+}
+
+static void
+rtree_full (struct rtree *rtree)
+{
+    rtree->available = NULL;
+}
+
+void gimp_display_shell_xfer_init (GimpDisplayShell *shell, int w, int h)
+{
+    rtree_init (&shell->xfer, w, h);
+}
+
+void gimp_display_shell_xfer_realize (GimpDisplayShell *shell)
+{
+    cairo_t *cr;
+
+    gimp_display_shell_xfer_fini (shell);
+
+    cr = gdk_cairo_create (gtk_widget_get_window (GTK_WIDGET (shell->canvas)));
+    shell->render_surface =
+	cairo_surface_create_similar_image (cairo_get_target  (cr),
+					    CAIRO_FORMAT_ARGB32,
+					    shell->xfer.root.w,
+					    shell->xfer.root.h);
+    cairo_destroy (cr);
+}
+
+void gimp_display_shell_xfer_fini (GimpDisplayShell *shell)
+{
+  if (shell->render_surface)
+    {
+      cairo_surface_destroy (shell->render_surface);
+      shell->render_surface = NULL;
+    }
+    rtree_reset (&shell->xfer);
+}
+
+static cairo_surface_t *
+get_transport_surface (GimpDisplayShell *shell,
+		       gint w, gint h)
+{
+    struct rtree_node *node;
+    cairo_surface_t *xfer;
+    unsigned char *data;
+    int stride;
+
+    node = rtree_insert (&shell->xfer, w, h);
+    if (node == NULL) {
+	cairo_surface_flush (shell->render_surface);
+	rtree_reset (&shell->xfer);
+	cairo_surface_mark_dirty (shell->render_surface); /* XXX */
+	node = rtree_insert (&shell->xfer, w, h);
+    }
+
+    stride = cairo_image_surface_get_stride (shell->render_surface);
+    data = cairo_image_surface_get_data (shell->render_surface);
+    data += node->y * stride + node->x * 4;
+
+    xfer = cairo_image_surface_create_for_data (data, CAIRO_FORMAT_ARGB32,
+						w, h, stride);
+    if (cairo_surface_status (xfer)) {
+	cairo_surface_flush (shell->render_surface);
+	rtree_reset (&shell->xfer);
+	cairo_surface_mark_dirty (shell->render_surface);
+	rtree_full (&shell->xfer);
+	return cairo_surface_reference (shell->render_surface);
+    }
+
+    return xfer;
+}
 
 void
 gimp_display_shell_render (GimpDisplayShell *shell,
@@ -59,6 +252,7 @@ gimp_display_shell_render (GimpDisplayShell *shell,
   gint            viewport_offset_y;
   gint            viewport_width;
   gint            viewport_height;
+  cairo_surface_t *xfer;
 
   g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
   g_return_if_fail (cr != NULL);
@@ -80,6 +274,7 @@ gimp_display_shell_render (GimpDisplayShell *shell,
                                                  &viewport_offset_y,
                                                  &viewport_width,
                                                  &viewport_height);
+  xfer = get_transport_surface (shell, w * window_scale, h * window_scale);
 
   gegl_buffer_get (buffer,
                    GEGL_RECTANGLE ((x + viewport_offset_x) * window_scale,
@@ -88,32 +283,13 @@ gimp_display_shell_render (GimpDisplayShell *shell,
                                    h * window_scale),
                    shell->scale_x * window_scale,
                    babl_format ("cairo-ARGB32"),
-                   cairo_image_surface_get_data (shell->render_surface),
-                   cairo_image_surface_get_stride (shell->render_surface),
+                   cairo_image_surface_get_data (xfer),
+                   cairo_image_surface_get_stride (xfer),
                    GEGL_ABYSS_NONE);
 
   /*  apply filters to the rendered projection  */
   if (shell->filter_stack)
-    {
-      cairo_surface_t *sub = shell->render_surface;
-
-      if (w != GIMP_DISPLAY_RENDER_BUF_WIDTH ||
-          h != GIMP_DISPLAY_RENDER_BUF_HEIGHT)
-        sub = cairo_image_surface_create_for_data (cairo_image_surface_get_data (sub),
-                                                   CAIRO_FORMAT_ARGB32,
-                                                   w * window_scale,
-                                                   h * window_scale,
-                                                   GIMP_DISPLAY_RENDER_BUF_WIDTH * 4);
-
-      gimp_color_display_stack_convert_surface (shell->filter_stack, sub);
-
-      if (sub != shell->render_surface)
-        cairo_surface_destroy (sub);
-    }
-
-  cairo_surface_mark_dirty_rectangle (shell->render_surface,
-                                      0, 0,
-                                      w * window_scale, h * window_scale);
+      gimp_color_display_stack_convert_surface (shell->filter_stack, xfer);
 
 #if 0
   if (shell->mask)
@@ -151,7 +327,7 @@ gimp_display_shell_render (GimpDisplayShell *shell,
 
   cairo_scale (cr, 1.0 / window_scale, 1.0 / window_scale);
 
-  cairo_set_source_surface (cr, shell->render_surface,
+  cairo_set_source_surface (cr, xfer,
                             x * window_scale,
                             y * window_scale);
 
@@ -167,4 +343,5 @@ gimp_display_shell_render (GimpDisplayShell *shell,
 #endif
 
   cairo_restore (cr);
+  cairo_surface_destroy (xfer);
 }
diff --git a/app/display/gimpdisplayshell-render.h b/app/display/gimpdisplayshell-render.h
index 652cddd..aad7f0a 100644
--- a/app/display/gimpdisplayshell-render.h
+++ b/app/display/gimpdisplayshell-render.h
@@ -38,5 +38,8 @@ void  gimp_display_shell_render (GimpDisplayShell *shell,
                                  gint              w,
                                  gint              h);
 
+void gimp_display_shell_xfer_init (GimpDisplayShell *shell, int w, int h);
+void gimp_display_shell_xfer_realize (GimpDisplayShell *shell);
+void gimp_display_shell_xfer_fini (GimpDisplayShell *shell);
 
 #endif  /*  __GIMP_DISPLAY_SHELL_RENDER_H__  */
diff --git a/app/display/gimpdisplayshell.c b/app/display/gimpdisplayshell.c
index 3e99799..029a024 100644
--- a/app/display/gimpdisplayshell.c
+++ b/app/display/gimpdisplayshell.c
@@ -299,11 +299,11 @@ gimp_display_shell_init (GimpDisplayShell *shell)
   shell->x_src_dec   = 1;
   shell->y_src_dec   = 1;
 
-  shell->render_surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
-                                                      GIMP_DISPLAY_RENDER_BUF_WIDTH *
-                                                      GIMP_DISPLAY_RENDER_MAX_SCALE,
-                                                      GIMP_DISPLAY_RENDER_BUF_HEIGHT *
-                                                      GIMP_DISPLAY_RENDER_MAX_SCALE);
+  gimp_display_shell_xfer_init (shell,
+				GIMP_DISPLAY_RENDER_BUF_WIDTH *
+				GIMP_DISPLAY_RENDER_MAX_SCALE,
+				GIMP_DISPLAY_RENDER_BUF_HEIGHT *
+				GIMP_DISPLAY_RENDER_MAX_SCALE);
 
   gimp_display_shell_items_init (shell);
 
@@ -783,11 +783,7 @@ gimp_display_shell_dispose (GObject *object)
       shell->filter_idle_id = 0;
     }
 
-  if (shell->render_surface)
-    {
-      cairo_surface_destroy (shell->render_surface);
-      shell->render_surface = NULL;
-    }
+  gimp_display_shell_xfer_fini (shell);
 
   if (shell->mask_surface)
     {
diff --git a/app/display/gimpdisplayshell.h b/app/display/gimpdisplayshell.h
index af825f8..6788189 100644
--- a/app/display/gimpdisplayshell.h
+++ b/app/display/gimpdisplayshell.h
@@ -114,6 +114,13 @@ struct _GimpDisplayShell
 
   GtkWidget         *statusbar;        /*  statusbar                          */
 
+  struct rtree {
+      struct rtree_node {
+	  struct rtree_node *children[4];
+	  struct rtree_node *next;
+	  int x, y, w, h;
+      } root, *available;
+  } xfer; /* track subregions of render_surface for efficient uploads */
   cairo_surface_t   *render_surface;   /*  buffer for rendering the image     */
   cairo_surface_t   *mask_surface;     /*  buffer for rendering the mask      */
   cairo_pattern_t   *checkerboard;     /*  checkerboard pattern               */
diff --git a/configure.ac b/configure.ac
index 4792277..d8176f7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -46,7 +46,7 @@ m4_define([glib_required_version], [2.32.0])
 m4_define([atk_required_version], [2.2.0])
 m4_define([gtk_required_version], [2.24.10])
 m4_define([gdk_pixbuf_required_version], [2.24.1])
-m4_define([cairo_required_version], [1.10.2])
+m4_define([cairo_required_version], [1.12.0])
 m4_define([cairo_pdf_required_version], [1.10.2])
 m4_define([pangocairo_required_version], [1.29.4])
 m4_define([fontconfig_required_version], [2.2.0])
-- 
1.7.10.4