UI: Make Region overlap slide instead of fade

Requested by @billreynish.
Increases the TIMESTEP to 60Hz to have smooth animation.

2 files changed, 29 insertions, 3 deletions

diff --git a/source/blender/editors/screen/screen_ops.c b/source/blender/editors/screen/screen_ops.c
index 53a878bd655..9c7e18b0889 100644
--- a/source/blender/editors/screen/screen_ops.c
+++ b/source/blender/editors/screen/screen_ops.c
@@ -4512,7 +4512,7 @@ typedef struct RegionAlphaInfo {
 } RegionAlphaInfo;
 
 #define TIMEOUT		0.1f
-#define TIMESTEP	0.05f
+#define TIMESTEP	(1.0f / 60.0f)
 
 float ED_region_blend_alpha(ARegion *ar)
 {
diff --git a/source/blender/windowmanager/intern/wm_draw.c b/source/blender/windowmanager/intern/wm_draw.c
index c8e0360ed88..d760780beb8 100644
--- a/source/blender/windowmanager/intern/wm_draw.c
+++ b/source/blender/windowmanager/intern/wm_draw.c
@@ -461,9 +461,35 @@ void wm_draw_region_blend(ARegion *ar, int view, bool blend)
 	GPUShader *shader = GPU_shader_get_builtin_shader(GPU_SHADER_2D_IMAGE_RECT_COLOR);
 	GPU_shader_bind(shader);
 
+	rcti rect_geo = ar->winrct;
+	rect_geo.xmax += 1;
+	rect_geo.ymax += 1;
+
+	rctf rect_tex;
+	rect_tex.xmin = halfx;
+	rect_tex.ymin = halfy;
+	rect_tex.xmax = 1.0f + halfx;
+	rect_tex.ymax = 1.0f + halfy;
+
+	float alpha_easing = 1.0f - alpha;
+	alpha_easing = 1.0f - alpha_easing * alpha_easing;
+
+	/* Slide vertical panels */
+	float ofs_x = BLI_rcti_size_x(&ar->winrct) * (1.0f - alpha_easing);
+	if (ar->alignment == RGN_ALIGN_RIGHT) {
+		rect_geo.xmin += ofs_x;
+		rect_tex.xmax *= alpha_easing;
+		alpha = 1.0f;
+	}
+	else if (ar->alignment == RGN_ALIGN_LEFT) {
+		rect_geo.xmax -= ofs_x;
+		rect_tex.xmin += 1.0f - alpha_easing;
+		alpha = 1.0f;
+	}
+
 	glUniform1i(GPU_shader_get_uniform(shader, "image"), 0);
-	glUniform4f(GPU_shader_get_uniform(shader, "rect_icon"), halfx, halfy, 1.0f + halfx, 1.0f + halfy);
-	glUniform4f(GPU_shader_get_uniform(shader, "rect_geom"), ar->winrct.xmin, ar->winrct.ymin, ar->winrct.xmax + 1, ar->winrct.ymax + 1);
+	glUniform4f(GPU_shader_get_uniform(shader, "rect_icon"), rect_tex.xmin, rect_tex.ymin, rect_tex.xmax, rect_tex.ymax);
+	glUniform4f(GPU_shader_get_uniform(shader, "rect_geom"), rect_geo.xmin, rect_geo.ymin, rect_geo.xmax, rect_geo.ymax);
 	glUniform4f(GPU_shader_get_builtin_uniform(shader, GPU_UNIFORM_COLOR), alpha, alpha, alpha, alpha);
 
 	GPU_draw_primitive(GPU_PRIM_TRI_STRIP, 4);