Fix exposure not working with canvas background on Compatibility.

drivers/gles3/effects/copy_effects.cpp

@@ -192,6 +192,18 @@ void CopyEffects::copy_screen(float p_multiply) {
 	draw_screen_triangle();
 }
 
+void CopyEffects::copy_with_exposure(float p_exposure, float p_multiply) {
+	bool success = copy.shader.version_bind_shader(copy.shader_version, CopyShaderGLES3::MODE_APPLY_LINEAR_EXPOSURE_TO_SRGB);
+	if (!success) {
+		return;
+	}
+
+	copy.shader.version_set_uniform(CopyShaderGLES3::EXPOSURE, p_exposure, copy.shader_version, CopyShaderGLES3::MODE_APPLY_LINEAR_EXPOSURE_TO_SRGB);
+	copy.shader.version_set_uniform(CopyShaderGLES3::MULTIPLY, p_multiply, copy.shader_version, CopyShaderGLES3::MODE_APPLY_LINEAR_EXPOSURE_TO_SRGB);
+
+	draw_screen_triangle();
+}
+
 void CopyEffects::copy_cube_to_rect(const Rect2 &p_rect) {
 	bool success = copy.shader.version_bind_shader(copy.shader_version, CopyShaderGLES3::MODE_CUBE_TO_OCTAHEDRAL);
 	if (!success) {

drivers/gles3/effects/copy_effects.h

@@ -65,6 +65,7 @@ public:
 	void copy_with_lens_distortion(const Rect2 &p_rect, float p_layer, const Vector2 &p_eye_center, float p_k1, float p_k2, float p_upscale, float p_aspect_ration, bool p_linear_to_srgb = false);
 	void copy_to_and_from_rect(const Rect2 &p_rect);
 	void copy_screen(float p_multiply = 1.0);
+	void copy_with_exposure(float p_exposure, float p_multiply);
 	void copy_cube_to_rect(const Rect2 &p_rect);
 	void copy_cube_to_panorama(float p_mip_level);
 	void bilinear_blur(GLuint p_source_texture, int p_mipmap_count, const Rect2i &p_region);

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -2455,6 +2455,7 @@ void RasterizerSceneGLES3::render_scene(const Ref<RenderSceneBuffers> &p_render_
 	bool draw_feed = false;
 	float sky_energy_multiplier = 1.0;
 	int camera_feed_id = -1;
+	bool apply_canvas_bg_exposure = false;
 
 	if (unlikely(get_debug_draw_mode() == RSE::VIEWPORT_DEBUG_DRAW_OVERDRAW)) {
 		clear_color = Color(0, 0, 0, 1); //in overdraw mode, BG should always be black
@@ -2494,6 +2495,7 @@ void RasterizerSceneGLES3::render_scene(const Ref<RenderSceneBuffers> &p_render_
 			} break;
 			case RSE::ENV_BG_CANVAS: {
 				draw_canvas = true;
+				apply_canvas_bg_exposure = !Math::is_equal_approx(tonemap_ubo.exposure, 1.0f);
 			} break;
 			case RSE::ENV_BG_KEEP: {
 				keep_color = true;
@@ -2573,6 +2575,7 @@ void RasterizerSceneGLES3::render_scene(const Ref<RenderSceneBuffers> &p_render_
 		fbo = GLES3::LightStorage::get_singleton()->reflection_probe_instance_get_framebuffer(render_data.reflection_probe, render_data.reflection_probe_pass);
 	} else {
 		rb->set_apply_environment_effects_in_post(apply_environment_effects_in_post);
+		rb->set_apply_canvas_bg_exposure(apply_canvas_bg_exposure);
 		fbo = rb->get_render_fbo();
 	}
 
@@ -2676,7 +2679,11 @@ void RasterizerSceneGLES3::render_scene(const Ref<RenderSceneBuffers> &p_render_
 		glActiveTexture(GL_TEXTURE0);
 		glBindTexture(rt->view_count > 1 ? GL_TEXTURE_2D_ARRAY : GL_TEXTURE_2D, rt->color);
 
-		copy_effects->copy_screen(render_data.luminance_multiplier);
+		if (apply_canvas_bg_exposure) {
+			copy_effects->copy_with_exposure(tonemap_ubo.exposure, render_data.luminance_multiplier);
+		} else {
+			copy_effects->copy_screen(render_data.luminance_multiplier);
+		}
 
 		scene_state.enable_gl_depth_test(true);
 		scene_state.enable_gl_depth_draw(true);

drivers/gles3/shaders/effects/copy.glsl

@@ -13,6 +13,7 @@ mode_mipmap = #define MODE_MIPMAP
 mode_simple_color = #define MODE_SIMPLE_COLOR \n#define USE_COPY_SECTION
 mode_cube_to_octahedral = #define CUBE_TO_OCTAHEDRAL \n#define USE_COPY_SECTION
 mode_cube_to_panorama = #define CUBE_TO_PANORAMA
+mode_apply_linear_exposure_to_srgb = #define MODE_SIMPLE_COPY \n#define MODE_MULTIPLY \n#define APPLY_LINEAR_EXPOSURE_TO_SRGB
 
 #[specializations]
 
@@ -104,6 +105,10 @@ uniform float upscale;
 uniform float aspect_ratio;
 #endif // APPLY_LENS_DISTORTION
 
+#ifdef APPLY_LINEAR_EXPOSURE_TO_SRGB
+uniform float exposure;
+#endif
+
 layout(location = 0) out vec4 frag_color;
 
 // This approximation expects non-negative input; negative input behaves poorly.
@@ -165,6 +170,12 @@ void main() {
 		color.rgb = linear_to_srgb(color.rgb);
 #endif
 
+#ifdef APPLY_LINEAR_EXPOSURE_TO_SRGB
+		color.rgb = srgb_to_linear(color.rgb);
+		color.rgb *= exposure;
+		color.rgb = linear_to_srgb(color.rgb);
+#endif
+
 #ifdef MODE_MULTIPLY
 		color *= multiply;
 #endif // MODE_MULTIPLY

drivers/gles3/storage/render_scene_buffers_gles3.cpp

@@ -189,7 +189,7 @@ void RenderSceneBuffersGLES3::_check_render_buffers() {
 
 	ERR_FAIL_COND(view_count == 0);
 
-	bool use_internal_buffer = scaling_3d_mode != RSE::VIEWPORT_SCALING_3D_MODE_OFF || apply_environment_effects_in_post;
+	bool use_internal_buffer = scaling_3d_mode != RSE::VIEWPORT_SCALING_3D_MODE_OFF || apply_environment_effects_in_post || apply_canvas_bg_exposure;
 	GLenum depth_format = GL_DEPTH24_STENCIL8;
 	uint32_t depth_format_size = 4;
 	bool use_multiview = view_count > 1;
@@ -563,6 +563,10 @@ void RenderSceneBuffersGLES3::set_apply_environment_effects_in_post(bool p_apply
 	apply_environment_effects_in_post = p_apply_in_post;
 }
 
+void RenderSceneBuffersGLES3::set_apply_canvas_bg_exposure(bool p_apply_canvas_bg_exposure) {
+	apply_canvas_bg_exposure = p_apply_canvas_bg_exposure;
+}
+
 void RenderSceneBuffersGLES3::check_glow_buffers() {
 	if (glow.levels[0].color != 0) {
 		// already have these setup..

drivers/gles3/storage/render_scene_buffers_gles3.h

@@ -50,6 +50,7 @@ public:
 	//bool use_debanding = false;
 	uint32_t view_count = 1;
 	bool apply_environment_effects_in_post = false;
+	bool apply_canvas_bg_exposure = false;
 
 	RID render_target;
 
@@ -107,6 +108,7 @@ public:
 	virtual void set_texture_mipmap_bias(float p_texture_mipmap_bias) override {}
 	virtual void set_use_debanding(bool p_use_debanding) override {}
 	void set_apply_environment_effects_in_post(bool p_apply_environment_effects_in_post);
+	void set_apply_canvas_bg_exposure(bool p_apply_canvas_bg_exposure);
 
 	void free_render_buffer_data();