libobs: Plumb linear alpha flag

Use union for backwards compatibility.

libobs/obs-internal.h

@@ -685,6 +685,7 @@ struct obs_source {
 	int async_channel_count;
 	long async_rotation;
 	bool async_flip;
+	bool async_linear_alpha;
 	bool async_active;
 	bool async_update_texture;
 	bool async_unbuffered;

libobs/obs-source.c

@@ -2019,7 +2019,9 @@ bool update_async_textures(struct obs_source *source,
 {
 	enum convert_type type;
 
-	source->async_flip = frame->flip;
+	source->async_flip = (frame->flags & OBS_SOURCE_FRAME_FLIP) != 0;
+	source->async_linear_alpha =
+		(frame->flags & OBS_SOURCE_FRAME_LINEAR_ALPHA) != 0;
 
 	if (source->async_gpu_conversion && texrender)
 		return update_async_texrender(source, frame, tex, texrender);
@@ -2070,9 +2072,11 @@ static void obs_source_draw_async_texture(struct obs_source *source)
 
 	if (def_draw) {
 		effect = obs_get_base_effect(OBS_EFFECT_DEFAULT);
-		const bool linear = gs_get_linear_srgb();
-		const char *tech_name = linear ? "DrawNonlinearAlpha" : "Draw";
-		premultiplied = linear;
+		const bool nonlinear_alpha = gs_get_linear_srgb() &&
+					     !source->async_linear_alpha;
+		const char *tech_name = nonlinear_alpha ? "DrawNonlinearAlpha"
+							: "Draw";
+		premultiplied = nonlinear_alpha;
 		tech = gs_effect_get_technique(effect, tech_name);
 		gs_technique_begin(tech);
 		gs_technique_begin_pass(tech, 0);
@@ -2720,7 +2724,7 @@ static inline void copy_frame_data_plane(struct obs_source_frame *dst,
 static void copy_frame_data(struct obs_source_frame *dst,
 			    const struct obs_source_frame *src)
 {
-	dst->flip = src->flip;
+	dst->flags = src->flags;
 	dst->full_range = src->full_range;
 	dst->timestamp = src->timestamp;
 	memcpy(dst->color_matrix, src->color_matrix, sizeof(float) * 16);
@@ -2951,7 +2955,7 @@ void obs_source_output_video2(obs_source_t *source,
 	new_frame.timestamp = frame->timestamp;
 	new_frame.format = frame->format;
 	new_frame.full_range = range == VIDEO_RANGE_FULL;
-	new_frame.flip = frame->flip;
+	new_frame.flags = frame->flags;
 
 	memcpy(&new_frame.color_matrix, &frame->color_matrix,
 	       sizeof(frame->color_matrix));
@@ -3082,7 +3086,7 @@ void obs_source_preload_video2(obs_source_t *source,
 	new_frame.timestamp = frame->timestamp;
 	new_frame.format = frame->format;
 	new_frame.full_range = range == VIDEO_RANGE_FULL;
-	new_frame.flip = frame->flip;
+	new_frame.flags = frame->flags;
 
 	memcpy(&new_frame.color_matrix, &frame->color_matrix,
 	       sizeof(frame->color_matrix));
@@ -3186,7 +3190,7 @@ void obs_source_set_video_frame2(obs_source_t *source,
 	new_frame.timestamp = frame->timestamp;
 	new_frame.format = frame->format;
 	new_frame.full_range = range == VIDEO_RANGE_FULL;
-	new_frame.flip = frame->flip;
+	new_frame.flags = frame->flags;
 
 	memcpy(&new_frame.color_matrix, &frame->color_matrix,
 	       sizeof(frame->color_matrix));

libobs/obs.h

@@ -219,6 +219,9 @@ struct obs_source_cea_708 {
 	uint64_t timestamp;
 };
 
+#define OBS_SOURCE_FRAME_FLIP (1 << 0)
+#define OBS_SOURCE_FRAME_LINEAR_ALPHA (1 << 1)
+
 /**
  * Source asynchronous video output structure.  Used with
  * obs_source_output_video to output asynchronous video.  Video is buffered as
@@ -244,7 +247,10 @@ struct obs_source_frame {
 	bool full_range;
 	float color_range_min[3];
 	float color_range_max[3];
-	bool flip;
+	union {
+		uint8_t flip : 1; /* deprecated */
+		uint8_t flags;
+	};
 
 	/* used internally by libobs */
 	volatile long refs;
@@ -263,7 +269,10 @@ struct obs_source_frame2 {
 	float color_matrix[16];
 	float color_range_min[3];
 	float color_range_max[3];
-	bool flip;
+	union {
+		uint8_t flip : 1; /* deprecated */
+		uint8_t flags;
+	};
 };
 
 /** Access to the argc/argv used to start OBS. What you see is what you get. */