gg: fix gg.draw_rounded_rect_filled() graphical abnormalities (#14128)

vlib/gg/draw.c.v

@@ -278,72 +278,114 @@ pub fn (ctx &Context) draw_rounded_rect_empty(x f32, y f32, w f32, h f32, radius
 // `x`,`y` is the top-left corner of the rectangle.
 // `w` is the width, `h` is the height .
 // `radius` is the radius of the corner-rounding in pixels.
-// `c` is the color of the outline.
+// `c` is the color of the filled.
 pub fn (ctx &Context) draw_rounded_rect_filled(x f32, y f32, w f32, h f32, radius f32, c gx.Color) {
+	assert w > 0 && h > 0 && radius >= 0
+	if c.a != 255 {
+		sgl.load_pipeline(ctx.timage_pip)
+	}
 	sgl.c4b(c.r, c.g, c.b, c.a)
-	sgl.begin_triangle_strip()
-	mut theta := f32(0)
 	mut xx := f32(0)
 	mut yy := f32(0)
-	r := radius * ctx.scale
+	mut radians := f32(0)
+	mut new_radius := radius
+	if w >= h && radius > h / 2 {
+		new_radius = h / 2
+	} else if radius > w / 2 {
+		new_radius = w / 2
+	}
+
+	r := new_radius * ctx.scale
 	nx := x * ctx.scale
 	ny := y * ctx.scale
 	width := w * ctx.scale
 	height := h * ctx.scale
-	segments := 2 * math.pi * r
-	segdiv := segments / 4
-	rb := 0
-	lb := int(rb + segdiv)
-	lt := int(lb + segdiv)
-	rt := int(lt + segdiv)
-	// left top
-	lx := nx + r
-	ly := ny + r
-	for i in lt .. rt {
-		theta = 2 * f32(math.pi) * f32(i) / segments
-		xx = r * math.cosf(theta)
-		yy = r * math.sinf(theta)
-		sgl.v2f(xx + lx, yy + ly)
-		sgl.v2f(lx, ly)
+
+	// left top quarter
+	sgl.begin_triangle_strip()
+	ltx := nx + r
+	lty := ny + r
+	for i in 0 .. 91 {
+		if r == 0 {
+			break
+		}
+		radians = f32(math.radians(i))
+		xx = r * math.cosf(radians)
+		yy = r * math.sinf(radians)
+		sgl.v2f(ltx - xx, lty - yy)
+		sgl.v2f(ltx, lty)
 	}
-	// right top
-	mut rx := nx + width - r
-	mut ry := ny + r
-	for i in rt .. int(segments) {
-		theta = 2 * f32(math.pi) * f32(i) / segments
-		xx = r * math.cosf(theta)
-		yy = r * math.sinf(theta)
-		sgl.v2f(xx + rx, yy + ry)
-		sgl.v2f(rx, ry)
+	sgl.end()
+
+	// right top quarter
+	sgl.begin_triangle_strip()
+	rtx := nx + width - r
+	rty := ny + r
+	for i in 0 .. 91 {
+		if r == 0 {
+			break
+		}
+		radians = f32(math.radians(i))
+		xx = r * math.cosf(radians)
+		yy = r * math.sinf(radians)
+		sgl.v2f(rtx + xx, rty - yy)
+		sgl.v2f(rtx, rty)
 	}
-	// right bottom
-	mut rbx := rx
-	mut rby := ny + height - r
-	for i in rb .. lb {
-		theta = 2 * f32(math.pi) * f32(i) / segments
-		xx = r * math.cosf(theta)
-		yy = r * math.sinf(theta)
-		sgl.v2f(xx + rbx, yy + rby)
+	sgl.end()
+
+	// right bottom quarter
+	sgl.begin_triangle_strip()
+	rbx := nx + width - r
+	rby := ny + height - r
+	for i in 0 .. 91 {
+		if r == 0 {
+			break
+		}
+		radians = f32(math.radians(i))
+		xx = r * math.cosf(radians)
+		yy = r * math.sinf(radians)
+		sgl.v2f(rbx + xx, rby + yy)
 		sgl.v2f(rbx, rby)
 	}
-	// left bottom
-	mut lbx := lx
-	mut lby := ny + height - r
-	for i in lb .. lt {
-		theta = 2 * f32(math.pi) * f32(i) / segments
-		xx = r * math.cosf(theta)
-		yy = r * math.sinf(theta)
-		sgl.v2f(xx + lbx, yy + lby)
+	sgl.end()
+
+	// left bottom quarter
+	sgl.begin_triangle_strip()
+	lbx := nx + r
+	lby := ny + height - r
+	for i in 0 .. 91 {
+		if r == 0 {
+			break
+		}
+		radians = f32(math.radians(i))
+		xx = r * math.cosf(radians)
+		yy = r * math.sinf(radians)
+		sgl.v2f(lbx - xx, lby + yy)
 		sgl.v2f(lbx, lby)
 	}
-	sgl.v2f(lx + xx, ly)
-	sgl.v2f(lx, ly)
 	sgl.end()
+
+	// Separate drawing is to prevent transparent color overlap
+	// top rectangle
+	sgl.begin_quads()
+	sgl.v2f(ltx, ny)
+	sgl.v2f(rtx, ny)
+	sgl.v2f(rtx, rty)
+	sgl.v2f(ltx, lty)
+	sgl.end()
+	// middle rectangle
+	sgl.begin_quads()
+	sgl.v2f(nx, ny + r)
+	sgl.v2f(rtx + r, rty)
+	sgl.v2f(rbx + r, rby)
+	sgl.v2f(nx, lby)
+	sgl.end()
+	// bottom rectangle
 	sgl.begin_quads()
-	sgl.v2f(lx, ly)
-	sgl.v2f(rx, ry)
-	sgl.v2f(rbx, rby)
 	sgl.v2f(lbx, lby)
+	sgl.v2f(rbx, rby)
+	sgl.v2f(rbx, ny + height)
+	sgl.v2f(lbx, ny + height)
 	sgl.end()
 }