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.

9 files changed, 37 insertions, 11 deletions

diff --git a/README.md b/README.md
index 418aab94..7fbd691a 100644
--- a/README.md
+++ b/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
diff --git a/examples/meson.build b/examples/meson.build
index 26d103bb..51e7d311 100644
--- a/examples/meson.build
+++ b/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)
diff --git a/include/wlr/config.h.in b/include/wlr/config.h.in
index 71868a34..0b612271 100644
--- a/include/wlr/config.h.in
+++ b/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
diff --git a/meson.build b/meson.build
index 5d45073d..971be7e6 100644
--- a/meson.build
+++ b/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,
diff --git a/meson_options.txt b/meson_options.txt
index 550acbe6..1a439a4d 100644
--- a/meson_options.txt
+++ b/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')
diff --git a/render/allocator/allocator.c b/render/allocator/allocator.c
index 83e836ae..6b96e023 100644
--- a/render/allocator/allocator.c
+++ b/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)) {
diff --git a/render/allocator/meson.build b/render/allocator/meson.build
index db17ccb2..f8e452df 100644
--- a/render/allocator/meson.build
+++ b/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',
 )
 
-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')
+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
diff --git a/render/gles2/renderer.c b/render/gles2/renderer.c
index 5ffd6f85..e7bfe0e0 100644
--- a/render/gles2/renderer.c
+++ b/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>
diff --git a/render/meson.build b/render/meson.build
index a1289ede..2bdcced8 100644
--- a/render/meson.build
+++ b/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()
-		wlr_deps += egl
+	gbm = dependency('gbm', required: 'gles2' in renderers)
+	if egl.found() and gbm.found()
+		wlr_deps += [egl, gbm]
 		wlr_files += files('egl.c')
 	endif
 	subdir('gles2')