Added Liang-Barsky Line Clipping

radio/src/thirdparty/libopenui/src/bitmapbuffer.cpp

@@ -331,7 +331,97 @@ void BitmapBuffer::drawVerticalLine(coord_t x, coord_t y, coord_t h, uint8_t pat
   }
 }
 
-void BitmapBuffer::drawLine(coord_t x1, coord_t y1, coord_t x2, coord_t y2, uint8_t pat, LcdFlags flags)
+//
+// Liang-barsky clipping algo
+//
+static float lb_max(float arr[], int n)
+{
+  float m = 0;
+  for (int i = 0; i < n; ++i)
+    if (m < arr[i]) m = arr[i];
+  return m;
+}
+
+// this function gives the minimum
+static float lb_min(float arr[], int n)
+{
+  float m = 1;
+  for (int i = 0; i < n; ++i)
+    if (m > arr[i]) m = arr[i];
+  return m;
+}
+
+bool BitmapBuffer::liangBarskyClipper(coord_t& x1, coord_t& y1, coord_t& x2, coord_t& y2)
+{
+  // defining variables
+  float p1 = -(x2 - x1);
+  float p2 = -p1;
+  float p3 = -(y2 - y1);
+  float p4 = -p3;
+
+  float q1 = x1 - xmin;
+  float q2 = xmax - x1;
+  float q3 = y1 - ymin;
+  float q4 = ymax - y1;
+
+  float posarr[5], negarr[5];
+  int posind = 1, negind = 1;
+  posarr[0] = 1;
+  negarr[0] = 0;
+
+  if ((p1 == 0 && q1 < 0) || (p2 == 0 && q2 < 0) || (p3 == 0 && q3 < 0) ||
+      (p4 == 0 && q4 < 0)) {
+    return false;
+  }
+
+  if (p1 != 0) {
+    float r1 = q1 / p1;
+    float r2 = q2 / p2;
+    if (p1 < 0) {
+      negarr[negind++] = r1;  // for negative p1, add it to negative array
+      posarr[posind++] = r2;  // and add p2 to positive array
+    } else {
+      negarr[negind++] = r2;
+      posarr[posind++] = r1;
+    }
+  }
+  if (p3 != 0) {
+    float r3 = q3 / p3;
+    float r4 = q4 / p4;
+    if (p3 < 0) {
+      negarr[negind++] = r3;
+      posarr[posind++] = r4;
+    } else {
+      negarr[negind++] = r4;
+      posarr[posind++] = r3;
+    }
+  }
+
+  float xn1, yn1, xn2, yn2;
+  float rn1, rn2;
+  rn1 = lb_max(negarr, negind);  // maximum of negative array
+  rn2 = lb_min(posarr, posind);  // minimum of positive array
+
+  if (rn1 > rn2) {  // reject
+    return false;
+  }
+
+  xn1 = x1 + p2 * rn1;
+  yn1 = y1 + p4 * rn1;  // computing new points
+
+  xn2 = x1 + p2 * rn2;
+  yn2 = y1 + p4 * rn2;
+
+  x1 = coord_t(xn1);
+  y1 = coord_t(yn1);
+  x2 = coord_t(xn2);
+  y2 = coord_t(yn2);
+
+  return true;
+}
+
+void BitmapBuffer::drawLine(coord_t x1, coord_t y1, coord_t x2, coord_t y2,
+                            uint8_t pat, LcdFlags flags)
 {
   // Offsets
   x1 += offsetX;
@@ -339,6 +429,9 @@ void BitmapBuffer::drawLine(coord_t x1, coord_t y1, coord_t x2, coord_t y2, uint
   x2 += offsetX;
   y2 += offsetY;
 
+  if (!liangBarskyClipper(x1, y1, x2, y2))
+    return;
+  
   // No 'opacity' here, only 'color'
   pixel_t color = COLOR_VAL(flags);
 

radio/src/thirdparty/libopenui/src/bitmapbuffer.h

@@ -426,6 +426,8 @@ class BitmapBuffer: public BitmapBufferBase<pixel_t>
     }
 
     void drawHorizontalLineAbs(coord_t x, coord_t y, coord_t w, uint8_t pat, LcdFlags flags, uint8_t opacity);
+
+    bool liangBarskyClipper(coord_t& x1, coord_t& y1, coord_t& x2, coord_t& y2);
 };
 
 extern BitmapBuffer * lcd;