Subject: bug#31288: 27.0.50; [PATCH] Make cairo build somewhat usable

From: Ari Roponen <[email-masked]>
Date: Fri, 27 Apr 2018 16:19:16 +0300

Attached are two patches to make --with-cairo builds more usable.

First patch tries to fix screen corruption, and the second patch allows
cairo builds to display images.

These patches are only slightly tested, but I hope they will be useful.

In GNU Emacs 27.0.50 (build 10, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-04-27 built on arirop
Repository revision: caa93364d47bd28633cc065e31dd5972a1e916d5
Windowing system distributor 'Fedora Project', version 11.0.11906000
System Description: Fedora 28 (Twenty Eight)

>From 3e93c1a5290bbed7a9b923e1a16f930ec0fbd74a Mon Sep 17 00:00:00 2001
From: Ari Roponen <[email-masked]>
Date: Fri, 27 Apr 2018 15:13:12 +0300
Subject: [PATCH 1/2] Fix cairo problems

* src/xterm.c (x_begin_cr_clip): Create image surface.
(x_update_end) [USE_CAIRO]: Disable GTK3-specific code for now.
(x_scroll_run) [USE_CAIRO]: Implement scrolling.
---
 src/xterm.c | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/src/xterm.c b/src/xterm.c
index 6ab4a03002..52fe24e0fb 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -360,17 +360,12 @@ x_begin_cr_clip (struct frame *f, GC gc)
 
       if (! FRAME_CR_SURFACE (f))
         {
-          cairo_surface_t *surface;
-          surface = cairo_xlib_surface_create (FRAME_X_DISPLAY (f),
-                                               FRAME_X_DRAWABLE (f),
-                                               FRAME_DISPLAY_INFO (f)->visual,
-                                               FRAME_PIXEL_WIDTH (f),
-                                               FRAME_PIXEL_HEIGHT (f));
-          cr = cairo_create (surface);
-          cairo_surface_destroy (surface);
-        }
-      else
-        cr = cairo_create (FRAME_CR_SURFACE (f));
+	  FRAME_CR_SURFACE (f) =
+	    cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
+					FRAME_PIXEL_WIDTH (f),
+					FRAME_PIXEL_HEIGHT (f));
+	}
+      cr = cairo_create (FRAME_CR_SURFACE (f));
       FRAME_CR_CONTEXT (f) = cr;
     }
   cairo_save (cr);
@@ -1236,7 +1231,8 @@ x_update_end (struct frame *f)
     {
       cairo_t *cr = 0;
       block_input();
-#if defined (USE_GTK) && defined (HAVE_GTK3)
+      /* FIXME */
+#if 0 && defined (USE_GTK) && defined (HAVE_GTK3)
       if (FRAME_GTK_WIDGET (f))
         {
           GdkWindow *w = gtk_widget_get_window (FRAME_GTK_WIDGET (f));
@@ -4271,7 +4267,26 @@ x_scroll_run (struct window *w, struct run *run)
   x_clear_cursor (w);
 
 #ifdef USE_CAIRO
-  SET_FRAME_GARBAGED (f);
+  if (FRAME_CR_CONTEXT (f))
+    {
+      cairo_surface_t *s = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
+						       width, height);
+      cairo_t *cr = cairo_create (s);
+      cairo_set_source_surface (cr, cairo_get_target (FRAME_CR_CONTEXT (f)),
+				-x, -from_y);
+      cairo_paint (cr);
+      cairo_destroy (cr);
+
+      cr = FRAME_CR_CONTEXT (f);
+      cairo_save (cr);
+      cairo_set_source_surface (cr, s, 0, to_y);
+      cairo_rectangle (cr, x, to_y, width, height);
+      cairo_fill (cr);
+      cairo_restore (cr);
+      cairo_surface_destroy (s);
+    } else {
+    SET_FRAME_GARBAGED (f);
+  }
 #else
   XCopyArea (FRAME_X_DISPLAY (f),
              FRAME_X_DRAWABLE (f), FRAME_X_DRAWABLE (f),
-- 
2.17.0

>From 6a379d983544b3e1b241860854646ca039724151 Mon Sep 17 00:00:00 2001
From: Ari Roponen <[email-masked]>
Date: Fri, 27 Apr 2018 15:14:36 +0300
Subject: [PATCH 2/2] Add partial image support for cairo builds

* src/image.c (lookup_rgb_color): Add cairo support.
(jpeg_load_body): Fix preprocessor symbol.  Move colors definition
into non-cairo part.
(imagemagick_load_image) [USE_CAIRO]: Add partial support for
cairo.
---
 src/image.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/image.c b/src/image.c
index 37416c1616..4c3f6c5ab0 100644
--- a/src/image.c
+++ b/src/image.c
@@ -4629,6 +4629,8 @@ lookup_rgb_color (struct frame *f, int r, int g, int b)
   return PALETTERGB (r >> 8, g >> 8, b >> 8);
 #elif defined HAVE_NS
   return RGB_TO_ULONG (r >> 8, g >> 8, b >> 8);
+#elif defined USE_CAIRO
+  return (0xffu << 24) | (r << 16) | (g << 8) | b;
 #else
   xsignal1 (Qfile_error,
 	    build_string ("This Emacs mishandles this image file type"));
@@ -6702,10 +6704,10 @@ jpeg_load_body (struct frame *f, struct image *img,
   FILE *volatile fp = NULL;
   JSAMPARRAY buffer;
   int row_stride, x, y;
-  unsigned long *colors;
   int width, height;
   int i, ir, ig, ib;
 #ifndef USE_CAIRO
+  unsigned long *colors;
   XImagePtr ximg = NULL;
 #endif
 
@@ -6823,7 +6825,7 @@ jpeg_load_body (struct frame *f, struct image *img,
     else
       ir = 0, ig = 0, ib = 0;
 
-#ifndef CAIRO
+#ifndef USE_CAIRO
     /* Use the color table mechanism because it handles colors that
        cannot be allocated nicely.  Such colors will be replaced with
        a default color, and we don't have to care about which colors
@@ -8551,6 +8553,9 @@ imagemagick_load_image (struct frame *f, struct image *img,
   double rotation;
   char hint_buffer[MaxTextExtent];
   char *filename_hint = NULL;
+#ifdef USE_CAIRO
+  void *data;
+#endif
 
   /* Initialize the ImageMagick environment.  */
   static bool imagemagick_initialized;
@@ -8751,6 +8756,19 @@ imagemagick_load_image (struct frame *f, struct image *img,
   /* We can now get a valid pixel buffer from the imagemagick file, if all
      went ok.  */
 
+#ifdef USE_CAIRO
+  data = xmalloc (width * height * 4);
+#ifdef HAVE_MAGICKEXPORTIMAGEPIXELS
+  MagickExportImagePixels (image_wand, 0, 0, width, height,
+			   "BGRA", CharPixel, data);
+#else
+  /* FIXME: Implement this. For now, make it white. */
+  memset(data, 0xff, width * height * 4);
+#endif
+  create_cairo_image_surface (img, data, width, height);
+  goto done;
+#endif /* USE_CAIRO */
+
   init_color_table ();
 
 #if defined (HAVE_MAGICKEXPORTIMAGEPIXELS) && ! defined (HAVE_NS)
@@ -8861,6 +8879,9 @@ imagemagick_load_image (struct frame *f, struct image *img,
   /* Put ximg into the image.  */
   image_put_x_image (f, img, ximg, 0);
 
+#ifdef USE_CAIRO
+ done:
+#endif
   /* Final cleanup. image_wand should be the only resource left. */
   DestroyMagickWand (image_wand);
   if (bg_wand) DestroyPixelWand (bg_wand);
-- 
2.17.0