[gtk] gtk-demo: Speed up the build

[Matthias Clasen <matthiasc src gnome org>]

commit 200a2f5c71734aaf832c065e2583af303668bc4c
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Sep 30 22:47:00 2021 -0400

    gtk-demo: Speed up the build
    
    Avoid serializing the gresource blob into a C string
    and running gcc over it. Instead, use ld to put it
    directly into an .o file and add it to the build.
    
    The build system machinations here were copied from
    gobject/tests/meson.build, and should ideally be part
    of the meson gnome module.

 demos/gtk-demo/meson.build | 67 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 63 insertions(+), 4 deletions(-)
---
diff --git a/demos/gtk-demo/meson.build b/demos/gtk-demo/meson.build
index 9201655988..cffe2503e2 100644
--- a/demos/gtk-demo/meson.build
+++ b/demos/gtk-demo/meson.build
@@ -156,10 +156,69 @@ demos_h = custom_target('gtk4 demo header',
   command: [ find_program('geninclude.py'), '@OUTPUT@', '@INPUT@' ],
 )
 
-gtkdemo_resources = gnome.compile_resources('gtkdemo_resources',
-  'demo.gresource.xml',
-  source_dir: '.',
-)
+objcopy_supports_add_symbol = false
+objcopy = find_program('objcopy', required : false)
+if objcopy.found()
+  objcopy_supports_add_symbol = run_command(objcopy, '--help').stdout().contains('--add-symbol')
+endif
+
+ld = find_program('ld', required : false)
+
+if build_machine.system() == 'linux' and objcopy.found() and objcopy_supports_add_symbol and ld.found()
+  glib_compile_resources = find_program('glib-compile-resources')
+
+  # Create the resource blob
+  gtkdemo_gresource = custom_target('gtkdemo.gresource',
+      input : 'demo.gresource.xml',
+      output : 'gtkdemo.gresource',
+      command : [glib_compile_resources,
+                 '--target=@OUTPUT@',
+                 '--sourcedir=' + meson.current_source_dir(),
+                 '--sourcedir=' + meson.current_build_dir(),
+                 '@INPUT@'])
+
+  # Create resource data file
+  gtkdemo_resources_c = custom_target('gtkdemo_resources.c',
+      input : 'demo.gresource.xml',
+      output : 'gtkdemo_resources.c',
+      command : [glib_compile_resources,
+                 '--target=@OUTPUT@',
+                 '--sourcedir=' + meson.current_source_dir(),
+                 '--sourcedir=' + meson.current_build_dir(),
+                 '--generate-source',
+                 '--external-data',
+                 '--c-name', '_g_binary_gtkdemo',
+                 '@INPUT@'])
+
+  # Create object file containing resource data
+  gtkdemo_resources_binary = custom_target('gtkdemo_resources.o',
+      input : gtkdemo_gresource,
+      output : 'gtkdemo_resources.o',
+      command : [ld,
+                 '-r',
+                 '-b','binary',
+                 '@INPUT@',
+                 '-o','@OUTPUT@'])
+
+  # Rename symbol to match the one in the C file
+  gtkdemo_resources_o = custom_target('gtkdemo_resources2.o',
+    input : gtkdemo_resources_binary,
+    output : 'gtkdemo_resources2.o',
+    command : [objcopy,
+                 '--add-symbol','_g_binary_gtkdemo_resource_data=.data:0',
+                 '@INPUT@',
+                 '@OUTPUT@'])
+
+  gtkdemo_resources = [
+      gtkdemo_resources_c,
+      gtkdemo_resources_o,
+    ]
+else
+  gtkdemo_resources = gnome.compile_resources('gtkdemo_resources',
+    'demo.gresource.xml',
+    source_dir: '.',
+  )
+endif
 
 # Use a subset of compiler flags
 demo_cflags = []