Add 'output render_bit_depth [8|10]' command

This makes it possible to hint to the renderer and backends how many
bits per channel the buffers that the compositor draws windows onto
should have. Renderers and backends may deviate from this if they
do not support the formats with higher bit depth.

1 files changed, 38 insertions, 0 deletions

diff --git a/sway/config/output.c b/sway/config/output.c
index 6d39c2f5..63c81382 100644
--- a/sway/config/output.c
+++ b/sway/config/output.c
@@ -1,5 +1,6 @@
 #define _POSIX_C_SOURCE 200809L
 #include <assert.h>
+#include <drm_fourcc.h>
 #include <stdbool.h>
 #include <string.h>
 #include <sys/socket.h>
@@ -67,6 +68,7 @@ struct output_config *new_output_config(const char *name) {
         oc->subpixel = WL_OUTPUT_SUBPIXEL_UNKNOWN;
         oc->max_render_time = -1;
         oc->adaptive_sync = -1;
+        oc->render_bit_depth = RENDER_BIT_DEPTH_DEFAULT;
         return oc;
 }
 
@@ -113,6 +115,9 @@ void merge_output_config(struct output_config *dst, struct output_config *src) {
         if (src->adaptive_sync != -1) {
                 dst->adaptive_sync = src->adaptive_sync;
         }
+        if (src->render_bit_depth != RENDER_BIT_DEPTH_DEFAULT) {
+                dst->render_bit_depth = src->render_bit_depth;
+        }
         if (src->background) {
                 free(dst->background);
                 dst->background = strdup(src->background);
@@ -351,6 +356,23 @@ static int compute_default_scale(struct wlr_output *output) {
         return 2;
 }
 
+/* Lists of formats to try, in order, when a specific render bit depth has
+ * been asked for. The second to last format in each list should always
+ * be XRGB8888, as a reliable backup in case the others are not available;
+ * the last should be DRM_FORMAT_INVALID, to indicate the end of the list. */
+static const uint32_t *bit_depth_preferences[] = {
+        [RENDER_BIT_DEPTH_8] = (const uint32_t []){
+                DRM_FORMAT_XRGB8888,
+                DRM_FORMAT_INVALID,
+        },
+        [RENDER_BIT_DEPTH_10] = (const uint32_t []){
+                DRM_FORMAT_XRGB2101010,
+                DRM_FORMAT_XBGR2101010,
+                DRM_FORMAT_XRGB8888,
+                DRM_FORMAT_INVALID,
+        },
+};
+
 static void queue_output_config(struct output_config *oc,
                 struct sway_output *output) {
         if (output == root->noop_output) {
@@ -437,6 +459,22 @@ static void queue_output_config(struct output_config *oc,
                         oc->adaptive_sync);
                 wlr_output_enable_adaptive_sync(wlr_output, oc->adaptive_sync == 1);
         }
+
+        if (oc && oc->render_bit_depth != RENDER_BIT_DEPTH_DEFAULT) {
+                const uint32_t *fmts = bit_depth_preferences[oc->render_bit_depth];
+                assert(fmts);
+
+                for (size_t i = 0; fmts[i] != DRM_FORMAT_INVALID; i++) {
+                        wlr_output_set_render_format(wlr_output, fmts[i]);
+                        if (wlr_output_test(wlr_output)) {
+                                break;
+                        }
+
+                        sway_log(SWAY_DEBUG, "Preferred output format 0x%08x "
+                                "failed to work, falling back to next in "
+                                "list, 0x%08x", fmts[i], fmts[i + 1]);
+                }
+        }
 }
 
 bool apply_output_config(struct output_config *oc, struct sway_output *output) {