[Renderers/SDL3] Add rounded corners rectangle functionality (#219)

examples/SDL3-simple-demo/main.c

@@ -33,9 +33,13 @@ static inline Clay_Dimensions SDL_MeasureText(Clay_StringSlice text, Clay_TextEl
     return (Clay_Dimensions) { (float) width, (float) height };
 }
 
-static void Label(Clay_String text)
+static void Label(const Clay_String text)
 {
-    CLAY(CLAY_LAYOUT({ .padding = {16, 8} }), CLAY_RECTANGLE({ .color = Clay_Hovered() ? COLOR_BLUE : COLOR_ORANGE })) {
+    CLAY(CLAY_LAYOUT({ .padding = {8, 8} }),
+        CLAY_RECTANGLE({
+            .color = Clay_Hovered() ? COLOR_BLUE : COLOR_ORANGE,
+            .cornerRadius = (Clay_CornerRadius){ 8, 8, 8, 8 },
+        })) {
         CLAY_TEXT(text, CLAY_TEXT_CONFIG({
            .textColor = { 255, 255, 255, 255 },
            .fontId = FONT_ID,

renderers/SDL3/README

@@ -1,6 +1,5 @@
 Please note, the SDL3 renderer is not 100% feature complete. It is currently missing:
 
-- Rounded rectangle corners
 - Borders
 - Images
 - Scroll / Scissor handling

renderers/SDL3/clay_renderer_SDL3.c

@@ -2,29 +2,143 @@
 #include <SDL3/SDL_main.h>
 #include <SDL3/SDL.h>
 #include <SDL3_ttf/SDL_ttf.h>
+#include <math.h> //needed to perform the rounded corners rendering
 
 /* This needs to be global because the "MeasureText" callback doesn't have a
  * user data parameter */
 static TTF_Font *gFonts[1];
 
+//all rendering is performed  by a single SDL call, avoiding multiple RenderRect + plumbing choice for circles.
+static void SDL_RenderRoundedRect(SDL_Renderer *renderer, const SDL_FRect rect, const float cornerRadius, const Clay_Color _color) {
+    /* Even in 4K this is enough for smooth curves (low radius or rect size coupled with
+     * no AA or low resolution might make it appear as jagged curves) */
+    const int NUM_CIRCLE_SEGMENTS = 16;
+
+    const SDL_FColor color = { _color.r/255, _color.g/255, _color.b/255, _color.a/255 };
+
+    int indexCount = 0, vertexCount = 0;
+
+    const float minRadius = fminf(rect.w, rect.h) / 2.0f;
+    const float clampedRadius = fminf(cornerRadius, minRadius);
+
+    int totalVertices = 4 + (4 * (NUM_CIRCLE_SEGMENTS * 2)) + 2*4;
+    int totalIndices = 6 + (4 * (NUM_CIRCLE_SEGMENTS * 3)) + 6*4;
+
+    SDL_Vertex vertices[totalVertices];
+    int indices[totalIndices];
+
+    //define center rectangle
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y + clampedRadius}, color, {0, 0} }; //0 center TL
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y + clampedRadius}, color, {1, 0} }; //1 center TR
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y + rect.h - clampedRadius}, color, {1, 1} }; //2 center BR
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y + rect.h - clampedRadius}, color, {0, 1} }; //3 center BL
+
+    indices[indexCount++] = 0;
+    indices[indexCount++] = 1;
+    indices[indexCount++] = 3;
+    indices[indexCount++] = 1;
+    indices[indexCount++] = 2;
+    indices[indexCount++] = 3;
+
+    //define rounded corners as triangle fans
+    const float step = M_PI_2 / NUM_CIRCLE_SEGMENTS;
+    for (int i = 0; i < NUM_CIRCLE_SEGMENTS; i++)
+    {
+        const float angle1 = (float)i * step;
+        const float angle2 = ((float)i + 1.0f) * step;
+
+        for (int j = 0; j < 4; j++) {  // Iterate over four corners
+            float cx, cy, signX, signY;
+
+            switch (j) {
+                case 0: cx = rect.x + clampedRadius; cy = rect.y + clampedRadius; signX = -1; signY = -1; break; // Top-left
+                case 1: cx = rect.x + rect.w - clampedRadius; cy = rect.y + clampedRadius; signX = 1; signY = -1; break; // Top-right
+                case 2: cx = rect.x + rect.w - clampedRadius; cy = rect.y + rect.h - clampedRadius; signX = 1; signY = 1; break; // Bottom-right
+                case 3: cx = rect.x + clampedRadius; cy = rect.y + rect.h - clampedRadius; signX = -1; signY = 1; break; // Bottom-left
+                default: SDL_LogError(SDL_LOG_CATEGORY_ERROR, "Invalid corner index"); return;
+            }
+
+            vertices[vertexCount++] = (SDL_Vertex){ {cx + cosf(angle1) * clampedRadius * signX, cy + sinf(angle1) * clampedRadius * signY}, color, {0, 0} };
+            vertices[vertexCount++] = (SDL_Vertex){ {cx + cosf(angle2) * clampedRadius * signX, cy + sinf(angle2) * clampedRadius * signY}, color, {0, 0} };
+
+            indices[indexCount++] = j;  // Connect to corresponding central rectangle vertex
+            indices[indexCount++] = vertexCount - 2;
+            indices[indexCount++] = vertexCount - 1;
+        }
+    }
+
+    //Define edge rectangles
+    // Top edge
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y}, color, {0, 0} }; //TL
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y}, color, {1, 0} }; //TR
+
+    indices[indexCount++] = 0;
+    indices[indexCount++] = vertexCount - 2; //TL
+    indices[indexCount++] = vertexCount - 1; //TR
+    indices[indexCount++] = 1;
+    indices[indexCount++] = 0;
+    indices[indexCount++] = vertexCount - 1; //TR
+    // Right edge
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w, rect.y + clampedRadius}, color, {1, 0} }; //RT
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w, rect.y + rect.h - clampedRadius}, color, {1, 1} }; //RB
+
+    indices[indexCount++] = 1;
+    indices[indexCount++] = vertexCount - 2; //RT
+    indices[indexCount++] = vertexCount - 1; //RB
+    indices[indexCount++] = 2;
+    indices[indexCount++] = 1;
+    indices[indexCount++] = vertexCount - 1; //RB
+    // Bottom edge
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y + rect.h}, color, {1, 1} }; //BR
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y + rect.h}, color, {0, 1} }; //BL
+
+    indices[indexCount++] = 2;
+    indices[indexCount++] = vertexCount - 2; //BR
+    indices[indexCount++] = vertexCount - 1; //BL
+    indices[indexCount++] = 3;
+    indices[indexCount++] = 2;
+    indices[indexCount++] = vertexCount - 1; //BL
+    // Left edge
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x, rect.y + rect.h - clampedRadius}, color, {0, 1} }; //LB
+    vertices[vertexCount++] = (SDL_Vertex){ {rect.x, rect.y + clampedRadius}, color, {0, 0} }; //LT
+
+    indices[indexCount++] = 3;
+    indices[indexCount++] = vertexCount - 2; //LB
+    indices[indexCount++] = vertexCount - 1; //LT
+    indices[indexCount++] = 0;
+    indices[indexCount++] = 3;
+    indices[indexCount++] = vertexCount - 1; //LT
+
+    // Render everything
+    SDL_RenderGeometry(renderer, NULL, vertices, vertexCount, indices, indexCount);
+}
+
+
 static void SDL_RenderClayCommands(SDL_Renderer *renderer, Clay_RenderCommandArray *rcommands)
 {
     for (size_t i = 0; i < rcommands->length; i++) {
         Clay_RenderCommand *rcmd = Clay_RenderCommandArray_Get(rcommands, i);
-        Clay_BoundingBox bounding_box = rcmd->boundingBox;
+        const Clay_BoundingBox bounding_box = rcmd->boundingBox;
         const SDL_FRect rect = { bounding_box.x, bounding_box.y, bounding_box.width, bounding_box.height };
 
         switch (rcmd->commandType) {
             case CLAY_RENDER_COMMAND_TYPE_RECTANGLE: {
-                Clay_RectangleElementConfig *config = rcmd->config.rectangleElementConfig;
-                Clay_Color color = config->color;
+                const Clay_RectangleElementConfig *config = rcmd->config.rectangleElementConfig;
+                const Clay_Color color = config->color;
+
                 SDL_SetRenderDrawColor(renderer, color.r, color.g, color.b, color.a);
-                SDL_RenderFillRect(renderer, &rect);
+                if (config->cornerRadius.topLeft > 0) {
+                    //const float radius = (config->cornerRadius.topLeft * 2) / (float)((bounding_box.width > bounding_box.height) ? bounding_box.height : bounding_box.width);
+                    //SDL_RenderRoundedRect(renderer, rect, radius, color);
+                    SDL_RenderRoundedRect(renderer, rect, config->cornerRadius.topLeft, color);
+                } else {
+                    SDL_RenderFillRect(renderer, &rect);
+                }
             } break;
             case CLAY_RENDER_COMMAND_TYPE_TEXT: {
-                Clay_TextElementConfig *config = rcmd->config.textElementConfig;
-                Clay_String *text = &rcmd->text;
-                SDL_Color color = { config->textColor.r, config->textColor.g, config->textColor.b, config->textColor.a };
+                const Clay_TextElementConfig *config = rcmd->config.textElementConfig;
+                const Clay_String *text = &rcmd->text;
+                const SDL_Color color = { config->textColor.r, config->textColor.g, config->textColor.b, config->textColor.a };
 
                 TTF_Font *font = gFonts[config->fontId];
                 SDL_Surface *surface = TTF_RenderText_Blended(font, text->chars, text->length, color);