Add arguments to set the desired resolution.

This adds the --desired-width and --desired-height arguments which
tell kmscon what resolution the user *desires*. They are specifically
called desired because it is not guaranteed that this resolution will
be used: it will only work if the exact width and height match a
supported mode as reported by the system, and it will only work in
DRM mode (kmscon does not generally support modesetting in fbdev).

Additionally, it might not be possible to use the mode if there is not
enough memory to store the framebuffers. Using `video=<width>x<height>` on
the kernel's command line was enough to make sure that sufficient memory
was available on my machine. In this case, if we try to use the desired
mode then the user will be presented with a blank screen.

In either of the above cases, kmscon will revert to using the default
mode, which is what kmscon always uses prior to this patch.

docs/man/kmscon.1.xml.in

@@ -482,6 +482,27 @@
                 only be used to debug render engines. (default: off)</para>
         </listitem>
       </varlistentry>
+
+      <varlistentry>
+        <term><option>--desired-width {pixels}</option></term>
+        <term><option>--desired-height {pixels}</option></term>
+        <listitem>
+          <para>Set the desired width and height of the output. The given width
+          and height must match a supported more exactly for this option to have
+          any effect; if there is no supported mode that matches exactly, or if there is
+          an error when using the desired mode, then the default mode (first valid mode
+          found) will be used.</para>
+
+          <para>Modesetting is only supported in DRM mode, so these options do
+          nothing with fbdev. However, fbset can still be used to externally set
+          the mode when fbdev is in use.</para>
+
+          <para>Other system components may need configuration in order to use the desired
+          mode effectively. For example, the `video={width}x{height}` kernel parameter may
+          be required in order to ensure that there is enough memory to store the
+          framebuffers for a large resolution.</para>
+        </listitem>
+      </varlistentry>
     </variablelist>
 
     <para>Font Options:</para>

src/kmscon_conf.c

@@ -136,12 +136,19 @@ static void print_help()
 		"\t                                  Create new terminal session\n"
 		"\n"
 		"Video Options:\n"
-		"\t    --drm                   [on]    Use DRM if available\n"
-		"\t    --hwaccel               [off]   Use 3D hardware-acceleration if\n"
-		"\t                                    available\n"
-		"\t    --gpus={all,aux,primary}[all]   GPU selection mode\n"
-		"\t    --render-engine <eng>   [-]     Console renderer\n"
-		"\t    --render-timing         [off]   Print renderer timing information\n"
+		"\t    --drm                     [on]    Use DRM if available\n"
+		"\t    --hwaccel                 [off]   Use 3D hardware-acceleration if\n"
+		"\t                                      available\n"
+		"\t    --gpus={all,aux,primary}  [all]   GPU selection mode\n"
+		"\t    --render-engine <eng>     [-]     Console renderer\n"
+		"\t    --render-timing           [off]   Print renderer timing information\n"
+		"\t    --desired-width <pixels>  [0]\n"
+		"\t    --desired-height <pixels> [0]     Set the desired width/height of\n"
+		"\t                                      the output. If the desired mode\n"
+		"\t                                      is not available or encounters an\n"
+		"\t                                      error, a default mode will be\n"
+		"\t                                      used. See the man page for\n"
+		"\t                                      additional details.\n"
 		"\n"
 		"Font Options:\n"
 		"\t    --font-engine <engine>  [pango]\n"
@@ -734,6 +741,8 @@ int kmscon_conf_new(struct conf_ctx **out)
 		CONF_OPTION_BOOL(0, "hwaccel", &conf->hwaccel, false),
 		CONF_OPTION(0, 0, "gpus", &conf_gpus, NULL, NULL, NULL, &conf->gpus, KMSCON_GPU_ALL),
 		CONF_OPTION_STRING(0, "render-engine", &conf->render_engine, NULL),
+		CONF_OPTION_UINT(0, "desired-width", &conf->desired_width, 0),
+		CONF_OPTION_UINT(0, "desired-height", &conf->desired_height, 0),
 
 		/* Font Options */
 		CONF_OPTION_STRING(0, "font-engine", &conf->font_engine, "pango"),

src/kmscon_conf.h

@@ -145,6 +145,9 @@ struct kmscon_conf_t {
 	unsigned int gpus;
 	/* render engine */
 	char *render_engine;
+	/* screen resolution */
+	unsigned int desired_width;
+	unsigned int desired_height;
 
 	/* Font Options */
 	/* font engine */

src/kmscon_main.c

@@ -367,13 +367,16 @@ static int app_seat_add_video(struct app_seat *seat,
 		mode = UTERM_VIDEO_FBDEV;
 	}
 
-	ret = uterm_video_new(&vid->video, seat->app->eloop, node, mode);
+	ret = uterm_video_new(&vid->video, seat->app->eloop, node, mode,
+			      seat->conf->desired_width, seat->conf->desired_height);
 	if (ret) {
 		if (mode == UTERM_VIDEO_DRM3D) {
 			log_info("cannot create drm3d device %s on seat %s (%d); trying drm2d mode",
 				 vid->node, seat->name, ret);
 			ret = uterm_video_new(&vid->video, seat->app->eloop,
-					      node, UTERM_VIDEO_DRM2D);
+					      node, UTERM_VIDEO_DRM2D,
+					      seat->conf->desired_width,
+					      seat->conf->desired_height);
 			if (ret)
 				goto err_node;
 		} else {

src/kmscon_terminal.c

@@ -114,6 +114,8 @@ static void do_clear_margins(struct screen *scr)
 				   sw, dh);
 }
 
+static int font_set(struct kmscon_terminal *term);
+
 static void do_redraw_screen(struct screen *scr)
 {
 	int ret;
@@ -129,6 +131,14 @@ static void do_redraw_screen(struct screen *scr)
 	kmscon_text_render(scr->txt);
 
 	ret = uterm_display_swap(scr->disp, false);
+
+	if (ret == -EAGAIN) {
+		uterm_display_deactivate(scr->disp);
+		uterm_display_activate(scr->disp, NULL);
+		font_set(scr->term);
+		ret = uterm_display_swap(scr->disp, false);
+	}
+
 	if (ret) {
 		log_warning("cannot swap display %p", scr->disp);
 		return;

src/uterm_drm_shared.c

@@ -362,6 +362,11 @@ int uterm_drm_display_swap(struct uterm_display *disp, uint32_t fb,
 		ret = drmModePageFlip(vdrm->fd, ddrm->crtc_id, fb,
 				      DRM_MODE_PAGE_FLIP_EVENT, disp);
 		if (ret) {
+			if (disp->desired_mode != disp->default_mode) {
+				disp->desired_mode = disp->default_mode;
+				log_debug("Unable to page-flip desired mode! Switching to default mode.");
+				return -EAGAIN;
+			}
 			log_error("cannot page-flip on DRM-CRTC (%d): %m",
 				  errno);
 			return -EFAULT;
@@ -616,9 +621,27 @@ static void bind_display(struct uterm_video *video, drmModeRes *res,
 		if (!disp->default_mode)
 			disp->default_mode = mode;
 
+		if (video->desired_width != 0 &&
+		    video->desired_height != 0 &&
+		    mode->ops->get_width(mode) == video->desired_width &&
+		    mode->ops->get_height(mode) == video->desired_height)
+			disp->desired_mode = mode;
+
 		uterm_mode_unref(mode);
 	}
 
+	if (!disp->desired_mode) {
+		disp->desired_mode = disp->default_mode;
+	}
+
+	log_debug("Default mode %dx%d",
+		  disp->default_mode->ops->get_width(disp->default_mode),
+		  disp->default_mode->ops->get_height(disp->default_mode));
+
+	log_debug("Desired mode %dx%d",
+		  disp->desired_mode->ops->get_width(disp->desired_mode),
+		  disp->desired_mode->ops->get_height(disp->desired_mode));
+
 	if (shl_dlist_empty(&disp->modes)) {
 		log_warn("no valid mode for display found");
 		ret = -EFAULT;

src/uterm_video.c

@@ -410,7 +410,7 @@ int uterm_display_activate(struct uterm_display *disp, struct uterm_mode *mode)
 		return -EINVAL;
 
 	if (!mode)
-		mode = disp->default_mode;
+		mode = disp->desired_mode;
 
 	return VIDEO_CALL(disp->ops->activate, 0, disp, mode);
 }
@@ -544,7 +544,8 @@ int uterm_display_fake_blendv(struct uterm_display *disp,
 
 SHL_EXPORT
 int uterm_video_new(struct uterm_video **out, struct ev_eloop *eloop,
-		    const char *node, const struct uterm_video_module *mod)
+		    const char *node, const struct uterm_video_module *mod,
+		    unsigned int desired_width, unsigned int desired_height)
 {
 	struct uterm_video *video;
 	int ret;
@@ -572,6 +573,9 @@ int uterm_video_new(struct uterm_video **out, struct ev_eloop *eloop,
 	if (ret)
 		goto err_hook;
 
+	video->desired_width = desired_width;
+	video->desired_height = desired_height;
+
 	ev_eloop_ref(video->eloop);
 	log_info("new device %p", video);
 	*out = video;

src/uterm_video.h

@@ -192,7 +192,8 @@ int uterm_display_fake_blendv(struct uterm_display *disp,
 /* video interface */
 
 int uterm_video_new(struct uterm_video **out, struct ev_eloop *eloop,
-		    const char *node, const struct uterm_video_module *mod);
+		    const char *node, const struct uterm_video_module *mod,
+		    unsigned int desired_width, unsigned int desired_height);
 void uterm_video_ref(struct uterm_video *video);
 void uterm_video_unref(struct uterm_video *video);
 

src/uterm_video_internal.h

@@ -118,6 +118,7 @@ struct uterm_display {
 	struct shl_hook *hook;
 	struct shl_dlist modes;
 	struct uterm_mode *default_mode;
+	struct uterm_mode *desired_mode;
 	struct uterm_mode *current_mode;
 	int dpms;
 
@@ -159,6 +160,9 @@ struct uterm_video {
 	struct shl_dlist displays;
 	struct shl_hook *hook;
 
+	unsigned int desired_width;
+	unsigned int desired_height;
+
 	const struct uterm_video_module *mod;
 	const struct video_ops *ops;
 	void *data;

tests/test_output.c

@@ -58,6 +58,8 @@ struct {
 	bool fbdev;
 	bool test;
 	char *dev;
+	unsigned int desired_width;
+	unsigned int desired_height;
 } output_conf;
 
 static int blit_outputs(struct uterm_video *video)
@@ -187,6 +189,8 @@ struct conf_option options[] = {
 	CONF_OPTION_BOOL(0, "fbdev", &output_conf.fbdev, false),
 	CONF_OPTION_BOOL(0, "test", &output_conf.test, false),
 	CONF_OPTION_STRING(0, "dev",  &output_conf.dev, NULL),
+	CONF_OPTION_UINT(0, "desired-width", &output_conf.desired_width, 0),
+	CONF_OPTION_UINT(0, "desired-height", &output_conf.desired_height, 0),
 };
 
 int main(int argc, char **argv)
@@ -215,12 +219,16 @@ int main(int argc, char **argv)
 
 	log_notice("Creating video object using %s...", node);
 
-	ret = uterm_video_new(&video, eloop, node, mode);
+	ret = uterm_video_new(&video, eloop, node, mode,
+			      output_conf.desired_width,
+			      output_conf.desired_height);
 	if (ret) {
 		if (mode == UTERM_VIDEO_DRM3D) {
 			log_notice("cannot create drm device; trying drm2d mode");
 			ret = uterm_video_new(&video, eloop, node,
-					      UTERM_VIDEO_DRM2D);
+					      UTERM_VIDEO_DRM2D,
+					      output_conf.desired_width,
+					      output_conf.desired_height);
 			if (ret)
 				goto err_exit;
 		} else {