[Renderers/SDL2] Added rounded corner borders and fixed other issues (#258)

renderers/SDL2/clay_renderer_SDL2.c

@@ -4,6 +4,10 @@
 #include <SDL_image.h>
 #include <stdio.h>
 
+#ifndef M_PI
+    #define M_PI 3.14159
+#endif
+
 #define CLAY_COLOR_TO_SDL_COLOR_ARGS(color) color.r, color.g, color.b, color.a
 
 typedef struct
@@ -48,8 +52,8 @@ static void SDL_RenderFillRoundedRect(SDL_Renderer* renderer, const SDL_FRect re
 
     int indexCount = 0, vertexCount = 0;
 
-    const float minRadius = SDL_min(rect.w, rect.h) / 2.0f;
+    const float maxRadius = SDL_min(rect.w, rect.h) / 2.0f;
-    const float clampedRadius = SDL_min(cornerRadius, minRadius);
+    const float clampedRadius = SDL_min(cornerRadius, maxRadius);
 
     const int numCircleSegments = SDL_max(NUM_CIRCLE_SEGMENTS, (int)clampedRadius * 0.5f);
 
@@ -141,6 +145,121 @@ static void SDL_RenderFillRoundedRect(SDL_Renderer* renderer, const SDL_FRect re
     SDL_RenderGeometry(renderer, NULL, vertices, vertexCount, indices, indexCount);
 }
 
+//all rendering is performed by a single SDL call, using twi sets of arcing triangles, inner and outer, that fit together; along with two tringles to fill the end gaps.
+void SDL_RenderCornerBorder(SDL_Renderer *renderer, Clay_BoundingBox* boundingBox, Clay_BorderRenderData* config, int cornerIndex, Clay_Color _color){
+    /////////////////////////////////
+    //The arc is constructed of outer triangles and inner triangles (if needed).
+    //First three vertices are first outer triangle's vertices
+    //Each two vertices after that are the inner-middle and second-outer vertex of 
+    //each outer triangle after the first, because there first-outer vertex is equal to the
+    //second-outer vertex of the previous triangle. Indices set accordingly.
+    //The final two vertices are the missing vertices for the first and last inner triangles (if needed)
+    //Everything is in clockwise order (CW).
+    /////////////////////////////////
+    const SDL_Color color = (SDL_Color) {
+        .r = (Uint8)_color.r,
+        .g = (Uint8)_color.g,
+        .b = (Uint8)_color.b,
+        .a = (Uint8)_color.a,
+    };
+
+    float centerX, centerY, outerRadius, clampedRadius, startAngle, borderWidth;
+    const float maxRadius = SDL_min(boundingBox->width, boundingBox->height) / 2.0f;
+    
+    SDL_Vertex vertices[512];
+    int indices[512];
+    int indexCount = 0, vertexCount = 0;
+
+    switch (cornerIndex) {
+        case(0):
+            startAngle = M_PI; 
+            outerRadius = SDL_min(config->cornerRadius.topLeft, maxRadius);
+            centerX = boundingBox->x + outerRadius; 
+            centerY = boundingBox->y + outerRadius; 
+            borderWidth = config->width.top;
+        break;
+        case(1):
+            startAngle = 3*M_PI/2;
+            outerRadius = SDL_min(config->cornerRadius.topRight, maxRadius);
+            centerX = boundingBox->x + boundingBox->width - outerRadius; 
+            centerY = boundingBox->y + outerRadius; 
+            borderWidth = config->width.top;
+            break;
+        case(2):
+            startAngle = 0;
+            outerRadius = SDL_min(config->cornerRadius.bottomRight, maxRadius);
+            centerX = boundingBox->x + boundingBox->width - outerRadius; 
+            centerY = boundingBox->y + boundingBox->height - outerRadius; 
+            borderWidth = config->width.bottom;
+            break;
+        case(3):
+            startAngle = M_PI/2;
+            outerRadius = SDL_min(config->cornerRadius.bottomLeft, maxRadius);
+            centerX = boundingBox->x + outerRadius; 
+            centerY = boundingBox->y + boundingBox->height - outerRadius; 
+            borderWidth = config->width.bottom;
+            break;
+        default: break;
+    }
+    
+    const float innerRadius = outerRadius - borderWidth;
+    const int minNumOuterTriangles = NUM_CIRCLE_SEGMENTS;
+    const int numOuterTriangles = SDL_max(minNumOuterTriangles, ceilf(outerRadius * 0.5f));
+    const float angleStep = M_PI / (2.0*(float)numOuterTriangles);
+
+    //outer triangles, in CW order
+    for (int i = 0; i < numOuterTriangles; i++) { 
+        float angle1 =  startAngle + i*angleStep; //first-outer vertex angle
+        float angle2 =  startAngle + ((float)i + 0.5) * angleStep; //inner-middle vertex angle
+        float angle3 =  startAngle + (i+1)*angleStep; // second-outer vertex angle
+
+        if( i == 0){ //first outer triangle
+            vertices[vertexCount++] = (SDL_Vertex){ {centerX + SDL_cosf(angle1) * outerRadius, centerY + SDL_sinf(angle1) * outerRadius}, color, {0, 0} }; //vertex index = 0
+        }
+        indices[indexCount++] = vertexCount - 1; //will be second-outer vertex of last outer triangle if not first outer triangle.
+
+        vertices[vertexCount++] = (innerRadius > 0)?
+            (SDL_Vertex){ {centerX + SDL_cosf(angle2) * (innerRadius), centerY + SDL_sinf(angle2) * (innerRadius)}, color, {0, 0}}:
+            (SDL_Vertex){ {centerX, centerY }, color, {0, 0}};
+        indices[indexCount++] = vertexCount - 1;
+
+        vertices[vertexCount++] = (SDL_Vertex){ {centerX + SDL_cosf(angle3) * outerRadius, centerY + SDL_sinf(angle3) * outerRadius}, color, {0, 0} };
+        indices[indexCount++] = vertexCount - 1;
+    }
+
+    if(innerRadius > 0){
+        // inner triangles in CW order (except the first and last)
+        for (int i = 0; i < numOuterTriangles - 1; i++){ //skip the last outer triangle
+            if(i==0){ //first outer triangle -> second inner triangle
+                indices[indexCount++] = 1; //inner-middle vertex of first outer triangle
+                indices[indexCount++] = 2; //second-outer vertex of first outer triangle
+                indices[indexCount++] = 3; //innder-middle vertex of second-outer triangle
+            }else{
+                int baseIndex = 3; //skip first outer triangle
+                indices[indexCount++] = baseIndex + (i-1)*2; // inner-middle vertex of current outer triangle
+                indices[indexCount++] = baseIndex + (i-1)*2 + 1; // second-outer vertex of current outer triangle
+                indices[indexCount++] = baseIndex + (i-1)*2 + 2; // inner-middle vertex of next outer triangle
+            }
+        }
+
+        float endAngle = startAngle + M_PI/2.0;
+
+        //last inner triangle
+        indices[indexCount++] = vertexCount - 2; //inner-middle vertex of last outer triangle
+        indices[indexCount++] = vertexCount - 1; //second-outer vertex of last outer triangle
+        vertices[vertexCount++] = (SDL_Vertex){ {centerX + SDL_cosf(endAngle) * innerRadius, centerY + SDL_sinf(endAngle) * innerRadius}, color, {0, 0} }; //missing vertex
+        indices[indexCount++] = vertexCount - 1; 
+        
+        // //first inner triangle
+        indices[indexCount++] = 0; //first-outer vertex of first outer triangle
+        indices[indexCount++] = 1; //inner-middle vertex of first outer triangle
+        vertices[vertexCount++] = (SDL_Vertex){ {centerX + SDL_cosf(startAngle) * innerRadius, centerY + SDL_sinf(startAngle) * innerRadius}, color, {0, 0} }; //missing vertex
+        indices[indexCount++] = vertexCount - 1; 
+    }
+
+    SDL_RenderGeometry(renderer, NULL, vertices, vertexCount, indices, indexCount);
+}
+
 SDL_Rect currentClippingRectangle;
 
 static void Clay_SDL2_Render(SDL_Renderer *renderer, Clay_RenderCommandArray renderCommands, SDL2_Font *fonts)
@@ -228,37 +347,76 @@ static void Clay_SDL2_Render(SDL_Renderer *renderer, Clay_RenderCommandArray ren
             }
             case CLAY_RENDER_COMMAND_TYPE_BORDER: {
                 Clay_BorderRenderData *config = &renderCommand->renderData.border;
+                SDL_SetRenderDrawColor(renderer, CLAY_COLOR_TO_SDL_COLOR_ARGS(config->color));
+
+                if(boundingBox.width > 0 & boundingBox.height > 0){
+                    const float maxRadius = SDL_min(boundingBox.width, boundingBox.height) / 2.0f;
 
                     if (config->width.left > 0) {
-                    SDL_SetRenderDrawColor(renderer, CLAY_COLOR_TO_SDL_COLOR_ARGS(config->color));
+                        const float clampedRadiusTop = SDL_min((float)config->cornerRadius.topLeft, maxRadius);
-                    SDL_FRect rect = { boundingBox.x, boundingBox.y + config->cornerRadius.topLeft, config->width.left, boundingBox.height - config->cornerRadius.topLeft - config->cornerRadius.bottomLeft };
+                        const float clampedRadiusBottom = SDL_min((float)config->cornerRadius.bottomLeft, maxRadius);
+                        SDL_FRect rect = { 
+                            boundingBox.x, 
+                            boundingBox.y + clampedRadiusTop, 
+                            (float)config->width.left, 
+                            (float)boundingBox.height - clampedRadiusTop - clampedRadiusBottom
+                        };
                         SDL_RenderFillRectF(renderer, &rect);
                     }
     
                     if (config->width.right > 0) {
-                    SDL_SetRenderDrawColor(renderer, CLAY_COLOR_TO_SDL_COLOR_ARGS(config->color));
+                        const float clampedRadiusTop = SDL_min((float)config->cornerRadius.topRight, maxRadius);
-                    SDL_FRect rect = { boundingBox.x + boundingBox.width - config->width.right, boundingBox.y + config->cornerRadius.topRight, config->width.right, boundingBox.height - config->cornerRadius.topRight - config->cornerRadius.bottomRight };
+                        const float clampedRadiusBottom = SDL_min((float)config->cornerRadius.bottomRight, maxRadius);
-                    SDL_RenderFillRectF(renderer, &rect);
+                        SDL_FRect rect = { 
-                }
+                            boundingBox.x + boundingBox.width - config->width.right,
-
+                            boundingBox.y + clampedRadiusTop,
-                if (config->width.right > 0) {
+                            (float)config->width.right,
-                    SDL_SetRenderDrawColor(renderer, CLAY_COLOR_TO_SDL_COLOR_ARGS(config->color));
+                            (float)boundingBox.height - clampedRadiusTop - clampedRadiusBottom
-                    SDL_FRect rect = { boundingBox.x + boundingBox.width - config->width.right, boundingBox.y + config->cornerRadius.topRight, config->width.right, boundingBox.height - config->cornerRadius.topRight - config->cornerRadius.bottomRight };
+                        };
                         SDL_RenderFillRectF(renderer, &rect);
                     }
     
                     if (config->width.top > 0) {
-                    SDL_SetRenderDrawColor(renderer, CLAY_COLOR_TO_SDL_COLOR_ARGS(config->color));
+                        const float clampedRadiusLeft = SDL_min((float)config->cornerRadius.topLeft, maxRadius);
-                    SDL_FRect rect = { boundingBox.x + config->cornerRadius.topLeft, boundingBox.y, boundingBox.width - config->cornerRadius.topLeft - config->cornerRadius.topRight, config->width.top };
+                        const float clampedRadiusRight = SDL_min((float)config->cornerRadius.topRight, maxRadius);
+                        SDL_FRect rect = { 
+                            boundingBox.x + clampedRadiusLeft, 
+                            boundingBox.y, 
+                            boundingBox.width - clampedRadiusLeft - clampedRadiusRight, 
+                            (float)config->width.top };
                         SDL_RenderFillRectF(renderer, &rect);
                     }
     
                     if (config->width.bottom > 0) {
-                    SDL_SetRenderDrawColor(renderer, CLAY_COLOR_TO_SDL_COLOR_ARGS(config->color));
+                        const float clampedRadiusLeft = SDL_min((float)config->cornerRadius.bottomLeft, maxRadius);
-                    SDL_FRect rect = { boundingBox.x + config->cornerRadius.bottomLeft, boundingBox.y + boundingBox.height - config->width.bottom, boundingBox.width - config->cornerRadius.bottomLeft - config->cornerRadius.bottomRight, config->width.bottom };
+                        const float clampedRadiusRight = SDL_min((float)config->cornerRadius.bottomRight, maxRadius);
+                        SDL_FRect rect = { 
+                            boundingBox.x + clampedRadiusLeft, 
+                            boundingBox.y + boundingBox.height - config->width.bottom, 
+                            boundingBox.width - clampedRadiusLeft - clampedRadiusRight, 
+                            (float)config->width.bottom 
+                        };
                         SDL_RenderFillRectF(renderer, &rect);
                     }
     
+                    //corner index: 0->3 topLeft -> CW -> bottonLeft
+                    if (config->width.top > 0 & config->cornerRadius.topLeft > 0) {
+                        SDL_RenderCornerBorder(renderer, &boundingBox, config, 0, config->color);
+                    }
+
+                    if (config->width.top > 0 & config->cornerRadius.topRight> 0) {
+                        SDL_RenderCornerBorder(renderer, &boundingBox, config, 1, config->color);
+                    }
+
+                    if (config->width.bottom > 0 & config->cornerRadius.bottomLeft > 0) {
+                        SDL_RenderCornerBorder(renderer, &boundingBox, config, 2, config->color);
+                    }
+
+                    if (config->width.bottom > 0 & config->cornerRadius.bottomLeft > 0) {
+                        SDL_RenderCornerBorder(renderer, &boundingBox, config, 3, config->color);
+                    }
+                }
+
                 break;
             }
             default: {