blendish: support for "join area" arrow overlay

blendish.h

@@ -406,6 +406,13 @@ void bndNodeBackground(NVGcontext *ctx, float x, float y, float w, float h,
 // the rectangle at origin (x,y) and size (w, h)
 void bndSplitterWidgets(NVGcontext *ctx, float x, float y, float w, float h);
 
+// Draw the join area overlay stencil into the rectangle
+// at origin (x,y) and size (w,h)
+// vertical is 0 or 1 and designates the arrow orientation, 
+// mirror is 0 or 1 and flips the arrow side
+void bndJoinAreaOverlay(NVGcontext *ctx, float x, float y, float w, float h,
+    int vertical, int mirror);
+
 ////////////////////////////////////////////////////////////////////////////////
         
 // Estimator Functions
@@ -1239,6 +1246,62 @@ void bndSplitterWidgets(NVGcontext *ctx, float x, float y, float w, float h) {
     nvgStroke(ctx);
 }
 
+void bndJoinAreaOverlay(NVGcontext *ctx, float x, float y, float w, float h,
+    int vertical, int mirror) {
+        
+    if (vertical) {
+        float u = w;
+        w = h; h = u;
+    }
+        
+    float s = (w<h)?w:h;
+        
+    float x0,y0,x1,y1;
+    if (mirror) {
+        x0 = x+w;
+        y0 = y+h;
+        x1 = x;
+        y1 = y;
+        s = -s;
+    } else {
+        x0 = x;
+        y0 = y;
+        x1 = x+w;
+        y1 = y+h;
+    }
+    
+    float yc = (y0+y1)*0.5f;
+    float s2 = s/2.0f;
+    float s4 = s/4.0f;
+    float s8 = s/8.0f;
+    float x4 = x0+s4;
+        
+    float points[][2] = {
+        { x0,y0 },
+        { x1,y0 },
+        { x1,y1 },
+        { x0,y1 },
+        { x0,yc+s8 },
+        { x4,yc+s8 },
+        { x4,yc+s4 },
+        { x0+s2,yc },      
+        { x4,yc-s4 },
+        { x4,yc-s8 },
+        { x0,yc-s8 }
+    };  
+        
+    nvgBeginPath(ctx);
+    int count = sizeof(points) / (sizeof(float)*2);
+    nvgMoveTo(ctx,points[0][vertical&1],points[0][(vertical&1)^1]);
+    for (int i = 1; i < count; ++i) {
+        nvgLineTo(ctx,points[i][vertical&1],points[i][(vertical&1)^1]);
+    }
+    //nvgClosePath(ctx);
+    
+    nvgFillColor(ctx, nvgRGBAf(0,0,0,0.3));
+    nvgFill(ctx);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 float bndLabelWidth(NVGcontext *ctx, int iconid, const char *label) {

example.cpp

@@ -485,6 +485,7 @@ void draw_noodles(NVGcontext *vg, int x, int y) {
 
 void draw(NVGcontext *vg, float w, float h) {
     bndBackground(vg, 0, 0, w, h);
+    
     bndSplitterWidgets(vg, 0, 0, w, h);
     
     int x = 10;
@@ -732,6 +733,16 @@ void draw(NVGcontext *vg, float w, float h) {
     
     uiLayout();
     drawUI(vg, 0, 0, 0);
+    
+    UIvec2 cursor = uiGetCursor();
+    cursor.x -= w/2;
+    cursor.y -= h/2;
+    if (abs(cursor.x) > (w/4)) {
+        bndJoinAreaOverlay(vg, 0, 0, w, h, 0, (cursor.x > 0));
+    } else if (abs(cursor.y) > (h/4)) {
+        bndJoinAreaOverlay(vg, 0, 0, w, h, 1, (cursor.y > 0));
+    }
+    
     uiProcess();
 }