gl-renderer: Replace clip_transformed() context with a clipping box

Simplify clip_transformed() by replacing its context parameter with a
clipping box parameter. The context struct is still used internally to
pass data around.

Since clip_transformed() doesn't take a context anymore, the clipping
boxes are now declared per test and stored along with the other vertex
data. That prepares the ground to add new tests using different boxes.

Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>

libweston/vertex-clipping.c

@@ -30,6 +30,12 @@
 #include "shared/helpers.h"
 #include "vertex-clipping.h"
 
+struct clip_context {
+	struct clip_vertex prev;
+	struct clip_vertex box[2];
+	struct clip_vertex *vertices;
+};
+
 WESTON_EXPORT_FOR_TESTS float
 float_difference(float a, float b)
 {
@@ -286,23 +292,25 @@ clip_polygon_bottom(struct clip_context *ctx, const struct polygon8 *src,
 }
 
 WESTON_EXPORT_FOR_TESTS int
-clip_transformed(struct clip_context *ctx,
+clip_transformed(const struct clip_vertex *polygon,
-		 const struct clip_vertex *polygon,
 		 size_t polygon_len,
+		 const struct clip_vertex box[2],
 		 struct clip_vertex *restrict vertices)
 {
+	struct clip_context ctx;
 	struct polygon8 p, tmp;
 	int i, n;
 
 	if (polygon_len > 8)
 		return -1;
 
+	memcpy(ctx.box, box, 2 * sizeof *box);
 	memcpy(p.pos, polygon, polygon_len * sizeof *polygon);
 	p.n = polygon_len;
-	tmp.n = clip_polygon_left(ctx, &p, tmp.pos);
+	tmp.n = clip_polygon_left(&ctx, &p, tmp.pos);
-	p.n = clip_polygon_right(ctx, &tmp, p.pos);
+	p.n = clip_polygon_right(&ctx, &tmp, p.pos);
-	tmp.n = clip_polygon_top(ctx, &p, tmp.pos);
+	tmp.n = clip_polygon_top(&ctx, &p, tmp.pos);
-	p.n = clip_polygon_bottom(ctx, &tmp, p.pos);
+	p.n = clip_polygon_bottom(&ctx, &tmp, p.pos);
 
 	/* Get rid of duplicate vertices */
 	vertices[0] = p.pos[0];
@@ -326,7 +334,6 @@ clip_quad(struct gl_quad *quad,
 	  const struct clip_vertex box[2],
 	  struct clip_vertex *restrict vertices)
 {
-	struct clip_context ctx;
 	int i, n;
 
 	/* Simple case: quad edges are parallel to clipping box edges, there
@@ -360,8 +367,7 @@ clip_quad(struct gl_quad *quad,
 	 * https://www.codeguru.com/cplusplus/polygon-clipping/
 	 * but without looking at any of that code.
 	 */
-	memcpy(&ctx.box, box, 2 * sizeof *box);
+	n = clip_transformed(quad->polygon, 4, box, vertices);
-	n = clip_transformed(&ctx, quad->polygon, 4, vertices);
 
 	if (n < 3)
 		return 0;

libweston/vertex-clipping.h

@@ -39,19 +39,13 @@ struct gl_quad {
 	bool axis_aligned;
 };
 
-struct clip_context {
-	struct clip_vertex prev;
-	struct clip_vertex box[2];
-	struct clip_vertex *vertices;
-};
-
 float
 float_difference(float a, float b);
 
 int
-clip_transformed(struct clip_context *ctx,
+clip_transformed(const struct clip_vertex *polygon,
-		 const struct clip_vertex *polygon,
 		 size_t polygon_len,
+		 const struct clip_vertex box[2],
 		 struct clip_vertex *restrict vertices);
 
 /*

tests/vertex-clip-test.c

@@ -43,26 +43,8 @@
 #define OUTSIDE_Y1 (BOUNDING_BOX_BOTTOM_Y - 1.0f)
 #define OUTSIDE_Y2 (BOUNDING_BOX_TOP_Y + 1.0f)
 
-static void
-populate_clip_context (struct clip_context *ctx)
-{
-	ctx->box[0].x = BOUNDING_BOX_LEFT_X;
-	ctx->box[0].y = BOUNDING_BOX_BOTTOM_Y;
-	ctx->box[1].x = BOUNDING_BOX_RIGHT_X;
-	ctx->box[1].y = BOUNDING_BOX_TOP_Y;
-}
-
-static int
-clip_polygon (struct clip_context *ctx,
-	      struct clip_vertex *polygon,
-	      int n,
-	      struct clip_vertex *vertices)
-{
-	populate_clip_context(ctx);
-	return clip_transformed(ctx, polygon, n, vertices);
-}
-
 struct vertex_clip_test_data {
+	struct clip_vertex box[2];
 	struct clip_vertex polygon[8];
 	struct clip_vertex clipped[8];
 	int polygon_n;
@@ -72,6 +54,10 @@ struct vertex_clip_test_data {
 const struct vertex_clip_test_data test_data[] = {
 	/* All inside */
 	{
+		.box = {
+			{ BOUNDING_BOX_LEFT_X, BOUNDING_BOX_BOTTOM_Y },
+			{ BOUNDING_BOX_RIGHT_X, BOUNDING_BOX_TOP_Y },
+		},
 		.polygon = {
 			{ INSIDE_X1, INSIDE_Y1 },
 			{ INSIDE_X2, INSIDE_Y1 },
@@ -90,6 +76,10 @@ const struct vertex_clip_test_data test_data[] = {
 
 	/* Top outside */
 	{
+		.box = {
+			{ BOUNDING_BOX_LEFT_X, BOUNDING_BOX_BOTTOM_Y },
+			{ BOUNDING_BOX_RIGHT_X, BOUNDING_BOX_TOP_Y },
+		},
 		.polygon = {
 			{ INSIDE_X1, INSIDE_Y1 },
 			{ INSIDE_X2, INSIDE_Y1 },
@@ -108,6 +98,10 @@ const struct vertex_clip_test_data test_data[] = {
 
 	/* Bottom outside */
 	{
+		.box = {
+			{ BOUNDING_BOX_LEFT_X, BOUNDING_BOX_BOTTOM_Y },
+			{ BOUNDING_BOX_RIGHT_X, BOUNDING_BOX_TOP_Y },
+		},
 		.polygon = {
 			{ INSIDE_X1, OUTSIDE_Y1 },
 			{ INSIDE_X2, OUTSIDE_Y1 },
@@ -126,6 +120,10 @@ const struct vertex_clip_test_data test_data[] = {
 
 	/* Left outside */
 	{
+		.box = {
+			{ BOUNDING_BOX_LEFT_X, BOUNDING_BOX_BOTTOM_Y },
+			{ BOUNDING_BOX_RIGHT_X, BOUNDING_BOX_TOP_Y }
+		},
 		.polygon = {
 			{ OUTSIDE_X1, INSIDE_Y1 },
 			{ INSIDE_X2, INSIDE_Y1 },
@@ -144,6 +142,10 @@ const struct vertex_clip_test_data test_data[] = {
 
 	/* Right outside */
 	{
+		.box = {
+			{ BOUNDING_BOX_LEFT_X, BOUNDING_BOX_BOTTOM_Y },
+			{ BOUNDING_BOX_RIGHT_X, BOUNDING_BOX_TOP_Y },
+		},
 		.polygon = {
 			{ INSIDE_X1, INSIDE_Y1 },
 			{ OUTSIDE_X2, INSIDE_Y1 },
@@ -162,6 +164,10 @@ const struct vertex_clip_test_data test_data[] = {
 
 	/* Diamond extending from bounding box edges */
 	{
+		.box = {
+			{ BOUNDING_BOX_LEFT_X, BOUNDING_BOX_BOTTOM_Y },
+			{ BOUNDING_BOX_RIGHT_X, BOUNDING_BOX_TOP_Y },
+		},
 		.polygon = {
 			{ BOUNDING_BOX_LEFT_X - 25, BOUNDING_BOX_BOTTOM_Y + 25 },
 			{ BOUNDING_BOX_LEFT_X + 25, BOUNDING_BOX_TOP_Y + 25 },
@@ -180,6 +186,10 @@ const struct vertex_clip_test_data test_data[] = {
 
 	/* Diamond inside of bounding box edges */
 	{
+		.box = {
+			{ BOUNDING_BOX_LEFT_X, BOUNDING_BOX_BOTTOM_Y },
+			{ BOUNDING_BOX_RIGHT_X, BOUNDING_BOX_TOP_Y },
+		},
 		.polygon = {
 			{ BOUNDING_BOX_LEFT_X - 12.5, BOUNDING_BOX_BOTTOM_Y + 25 },
 			{ BOUNDING_BOX_LEFT_X + 25, BOUNDING_BOX_TOP_Y + 12.5 },
@@ -204,12 +214,11 @@ const struct vertex_clip_test_data test_data[] = {
 TEST_P(clip_polygon_n_vertices_emitted, test_data)
 {
 	struct vertex_clip_test_data *tdata = data;
-	struct clip_context ctx;
 	struct clip_vertex clipped[8];
 	int clipped_n;
 
-	clipped_n = clip_polygon(&ctx, tdata->polygon, tdata->polygon_n,
+	clipped_n = clip_transformed(tdata->polygon, tdata->polygon_n,
-				 clipped);
+				     tdata->box, clipped);
 
 	assert(clipped_n == tdata->clipped_n);
 }
@@ -217,12 +226,11 @@ TEST_P(clip_polygon_n_vertices_emitted, test_data)
 TEST_P(clip_polygon_expected_vertices, test_data)
 {
 	struct vertex_clip_test_data *tdata = data;
-	struct clip_context ctx;
 	struct clip_vertex clipped[8];
 	int clipped_n, i;
 
-	clipped_n = clip_polygon(&ctx, tdata->polygon, tdata->polygon_n,
+	clipped_n = clip_transformed(tdata->polygon, tdata->polygon_n,
-				 clipped);
+				     tdata->box, clipped);
 
 	for (i = 0; i < clipped_n; i++) {
 		assert(clipped[i].x == tdata->clipped[i].x);
@@ -232,10 +240,9 @@ TEST_P(clip_polygon_expected_vertices, test_data)
 
 TEST(clip_transformed_size_too_high)
 {
-	struct clip_context ctx;
+	struct clip_vertex polygon[8] = {}, box[2] = {};
-	struct clip_vertex polygon[8] = {};
 
-	assert(clip_transformed(&ctx, polygon, 9, NULL) == -1);
+	assert(clip_transformed(polygon, 9, box, NULL) == -1);
 }
 
 TEST(float_difference_different)