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

[Ari Roponen]

Eli Zaretskii <eliz@gnu.org> writes:

>
> Please allow me a couple of minor comments on the changes:
>
>> @@ -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));
>
> This hunk doesn't look right.  If the code in question causes some
> trouble to a Cairo build, please ifdef it out only when USE_CAIRO is
> defined, not unconditionally.  And if that still needs a FIXME
> comment, please add some description of what needs to be fixed and
> why.
>

That hunk is inside #ifdef USE_CAIRO, like almost the whole body of
x_update_end.

>> +      cairo_surface_destroy (s);
>> +    } else {
>> +    SET_FRAME_GARBAGED (f);
>
> Please use GNU style of braces.
>

Done. New patch attached.

>From dd7b085d569be5f1eb4412e28ac73f3f304eeb0f Mon Sep 17 00:00:00 2001
From: Ari Roponen <ari.roponen@gmail.com>
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 | 43 ++++++++++++++++++++++++++++++-------------
 1 file changed, 30 insertions(+), 13 deletions(-)

diff --git a/src/xterm.c b/src/xterm.c
index 6ab4a03002..2a1c7e9edc 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 +4267,28 @@ 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