build: make GBM optional

Now that the DRM backend no longer depends on GBM, we can make it
optional. The GLES2 renderer still depends on it because of our EGL
device selection.

This is useful for compositors with their own renderers, and for
compositors using the Vulkan renderer.

README.md

@@ -45,7 +45,7 @@ Install dependencies:
 * EGL and GLESv2 (optional, for the GLES2 renderer)
 * Vulkan loader, headers and glslang (optional, for the Vulkan renderer)
 * libdrm
-* GBM
+* GBM (optional, for the GBM allocator)
 * libinput (optional, for the libinput backend)
 * xkbcommon
 * udev

examples/meson.build

@@ -5,6 +5,7 @@ wayland_client = dependency('wayland-client')
 libpng = dependency('libpng', required: false, disabler: true)
 egl = dependency('egl', required: false, disabler: true)
 glesv2 = dependency('glesv2', required: false, disabler: true)
+gbm = dependency('gbm', required: false, disabler: true)
 # These versions correspond to ffmpeg 4.0
 libavutil = dependency('libavutil', version: '>=56.14.100', required: false, disabler: true)
 libavcodec = dependency('libavcodec', version: '>=58.18.100', required: false, disabler: true)

include/wlr/config.h.in

@@ -6,9 +6,10 @@
 #mesondefine WLR_HAS_X11_BACKEND
 
 #mesondefine WLR_HAS_GLES2_RENDERER
-
 #mesondefine WLR_HAS_VULKAN_RENDERER
 
+#mesondefine WLR_HAS_GBM_ALLOCATOR
+
 #mesondefine WLR_HAS_XWAYLAND
 
 #endif

meson.build

@@ -92,6 +92,7 @@ features = {
 	'xwayland': false,
 	'gles2-renderer': false,
 	'vulkan-renderer': false,
+	'gbm-allocator': false,
 }
 internal_features = {
 	'xcb-errors': false,
@@ -125,7 +126,6 @@ drm = dependency('libdrm',
 		'valgrind=false',
 	],
 )
-gbm = dependency('gbm', version: '>=17.1.0')
 xkbcommon = dependency('xkbcommon')
 udev = dependency('libudev')
 pixman = dependency('pixman-1')
@@ -136,7 +136,6 @@ wlr_files = []
 wlr_deps = [
 	wayland_server,
 	drm,
-	gbm,
 	xkbcommon,
 	udev,
 	pixman,

meson_options.txt

@@ -4,3 +4,5 @@ option('examples', type: 'boolean', value: true, description: 'Build example app
 option('icon_directory', description: 'Location used to look for cursors (default: ${datadir}/icons)', type: 'string', value: '')
 option('renderers', type: 'array', choices: ['auto', 'gles2', 'vulkan'], value: ['auto'], description: 'Select built-in renderers')
 option('backends', type: 'array', choices: ['auto', 'drm', 'libinput', 'x11'], value: ['auto'], description: 'Select built-in backends')
+option('allocators', type: 'array', choices: ['auto', 'gbm'], value: ['auto'],
+	description: 'Select built-in allocators')

render/allocator/allocator.c

@@ -3,6 +3,7 @@
 #include <fcntl.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <wlr/config.h>
 #include <wlr/interfaces/wlr_buffer.h>
 #include <wlr/render/allocator.h>
 #include <wlr/util/log.h>
@@ -11,10 +12,13 @@
 #include "backend/backend.h"
 #include "render/allocator/allocator.h"
 #include "render/allocator/drm_dumb.h"
-#include "render/allocator/gbm.h"
 #include "render/allocator/shm.h"
 #include "render/wlr_renderer.h"
 
+#if WLR_HAS_GBM_ALLOCATOR
+#include "render/allocator/gbm.h"
+#endif
+
 void wlr_allocator_init(struct wlr_allocator *alloc,
 		const struct wlr_allocator_interface *impl, uint32_t buffer_caps) {
 	assert(impl && impl->destroy && impl->create_buffer);
@@ -94,6 +98,8 @@ struct wlr_allocator *allocator_autocreate_with_drm_fd(
 	uint32_t renderer_caps = renderer_get_render_buffer_caps(renderer);
 
 	struct wlr_allocator *alloc = NULL;
+
+#if WLR_HAS_GBM_ALLOCATOR
 	uint32_t gbm_caps = WLR_BUFFER_CAP_DMABUF;
 	if ((backend_caps & gbm_caps) && (renderer_caps & gbm_caps)
 			&& drm_fd >= 0) {
@@ -108,6 +114,7 @@ struct wlr_allocator *allocator_autocreate_with_drm_fd(
 		close(gbm_fd);
 		wlr_log(WLR_DEBUG, "Failed to create gbm allocator");
 	}
+#endif
 
 	uint32_t shm_caps = WLR_BUFFER_CAP_SHM | WLR_BUFFER_CAP_DATA_PTR;
 	if ((backend_caps & shm_caps) && (renderer_caps & shm_caps)) {

render/allocator/meson.build

@@ -1,9 +1,25 @@
+allocators = get_option('allocators')
+if 'auto' in allocators and get_option('auto_features').enabled()
+	allocators = ['gbm']
+elif 'auto' in renderers and get_option('auto_features').disabled()
+	allocators = []
+endif
+
 wlr_files += files(
 	'allocator.c',
-	'gbm.c',
 	'shm.c',
 	'drm_dumb.c',
 )
 
+gbm = disabler()
+if 'gbm' in allocators or 'auto' in allocators
+	gbm = dependency('gbm', version: '>=17.1.0', required: 'gbm' in allocators)
+endif
+if gbm.found()
+	wlr_files += files('gbm.c')
+	wlr_deps += gbm
+	features += { 'gbm-allocator': true }
+
 	has = cc.has_function('gbm_bo_get_fd_for_plane', dependencies: [gbm])
 	add_project_arguments('-DHAS_GBM_BO_GET_FD_FOR_PLANE=@0@'.format(has.to_int()), language: 'c')
+endif

render/gles2/renderer.c

@@ -1,6 +1,5 @@
 #include <assert.h>
 #include <drm_fourcc.h>
-#include <gbm.h>
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
 #include <stdint.h>

render/meson.build

@@ -16,8 +16,9 @@ wlr_files += files(
 
 if 'gles2' in renderers or 'auto' in renderers
 	egl = dependency('egl', required: 'gles2' in renderers)
-	if egl.found()
+	gbm = dependency('gbm', required: 'gles2' in renderers)
-		wlr_deps += egl
+	if egl.found() and gbm.found()
+		wlr_deps += [egl, gbm]
 		wlr_files += files('egl.c')
 	endif
 	subdir('gles2')