Fix possible memory leak in Fl_WinAPI_Screen_Driver::read_win_rectangle_unscaled()

Thanks to "fire-eggs" for spotting it.
Also minor optimisations in Fl_X11_Screen_Driver::read_win_rectangle_unscaled() and
Fl_Cocoa_Screen_Driver::read_win_rectangle_unscaled().

This closes PR #151.

src/drivers/Cocoa/Fl_Cocoa_Screen_Driver.cxx

@@ -342,7 +342,7 @@ void Fl_Cocoa_Screen_Driver::offscreen_size(Fl_Offscreen off, int &width, int &h
 Fl_RGB_Image *Fl_Cocoa_Screen_Driver::read_win_rectangle(int X, int Y, int w, int h, Fl_Window *window,
                                                          bool may_capture_subwins, bool *did_capture_subwins)
 {
-  int bpp, bpr, depth = 4;
+  int bpp, bpr;
   uchar *base, *p;
   if (!window) { // read from offscreen buffer
     float s = 1;
@@ -364,9 +364,9 @@ Fl_RGB_Image *Fl_Cocoa_Screen_Driver::read_win_rectangle(int X, int Y, int w, in
     // Copy the image from the off-screen buffer to the memory buffer.
     int idx, idy;  // Current X & Y in image
     uchar *pdst, *psrc;
-    p = new uchar[w * h * depth];
+    p = new uchar[w * h * 4];
     for (idy = Y, pdst = p; idy < h + Y; idy ++) {
-      for (idx = 0, psrc = base + idy * bpr + X * bpp; idx < w; idx ++, psrc += bpp, pdst += depth) {
+      for (idx = 0, psrc = base + idy * bpr + X * bpp; idx < w; idx ++, psrc += bpp, pdst += 4) {
         pdst[0] = psrc[0];  // R
         pdst[1] = psrc[1];  // G
         pdst[2] = psrc[2];  // B
@@ -397,7 +397,7 @@ Fl_RGB_Image *Fl_Cocoa_Screen_Driver::read_win_rectangle(int X, int Y, int w, in
     delete surf;
     CFRelease(cgimg);
   }
-  Fl_RGB_Image *rgb = new Fl_RGB_Image(p, w, h, depth, bpr);
+  Fl_RGB_Image *rgb = new Fl_RGB_Image(p, w, h, 4, bpr);
   rgb->alloc_array = 1;
   return rgb;
 }

src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx

@@ -503,14 +503,7 @@ Fl_WinAPI_Screen_Driver::read_win_rectangle(
 
 Fl_RGB_Image *Fl_WinAPI_Screen_Driver::read_win_rectangle_unscaled(int X, int Y, int w, int h, Fl_Window *win)
 {
-  int   d = 3;                  // Depth of image
-  int alpha = 0; uchar *p = NULL;
-  // Allocate the image data array as needed...
-  const uchar *oldp = p;
-  if (!p) p = new uchar[w * h * d];
-
-  // Initialize the default colors/alpha in the whole image...
-  memset(p, alpha, w * h * d);
+  // Depth of image is always 3 here
   
   // Grab all of the pixels in the image...
 
@@ -534,7 +527,12 @@ Fl_RGB_Image *Fl_WinAPI_Screen_Driver::read_win_rectangle_unscaled(int X, int Y,
     Y = 0;
   }
 
-  if (h < 1 || w < 1) return 0/*p*/;            // nothing to copy
+  if (h < 1 || w < 1) return 0;            // nothing to copy
+  
+  // Allocate and initialize the image data array
+  size_t arraySize = ((size_t)w * h) * 3;
+  uchar *p = new uchar[arraySize];
+  memset(p, 0, arraySize);
 
   int line_size = ((3*w+3)/4) * 4;      // each line is aligned on a DWORD (4 bytes)
   uchar *dib = new uchar[line_size*h];  // create temporary buffer to read DIB
@@ -572,15 +570,13 @@ Fl_RGB_Image *Fl_WinAPI_Screen_Driver::read_win_rectangle_unscaled(int X, int Y,
 
   for (int j = 0; j<h; j++) {
     const uchar *src = dib + j * line_size;                     // source line
-    uchar *tg = p + (j + shift_y) * d * ww + shift_x * d;       // target line
+    uchar *tg = p + (j + shift_y) * 3 * ww + shift_x * 3;       // target line
     for (int i = 0; i<w; i++) {
       uchar b = *src++;
       uchar g = *src++;
       *tg++ = *src++;   // R
       *tg++ = g;        // G
       *tg++ = b;        // B
-      if (alpha)
-        *tg++ = alpha;  // alpha
     }
   }
 
@@ -591,8 +587,8 @@ Fl_RGB_Image *Fl_WinAPI_Screen_Driver::read_win_rectangle_unscaled(int X, int Y,
   DeleteObject(hbm);
   delete[] dib;         // delete DIB temporary buffer
 
-  Fl_RGB_Image *rgb = new Fl_RGB_Image(p, w, h, d);
-  if (!oldp) rgb->alloc_array = 1;
+  Fl_RGB_Image *rgb = new Fl_RGB_Image(p, w, h, 3);
+  rgb->alloc_array = 1;
   return rgb;
 }
 

src/drivers/X11/Fl_X11_Screen_Driver.cxx

@@ -750,7 +750,6 @@ Fl_RGB_Image *Fl_X11_Screen_Driver::read_win_rectangle(int X, int Y, int w, int
   XImage        *image;         // Captured image
   int           i, maxindex;    // Looping vars
   int           x, y;           // Current X & Y in image
-  int           d;              // Depth of image
   unsigned char *line,          // Array to hold image row
                 *line_ptr;      // Pointer to current line image
   unsigned char *pixel;         // Current color value
@@ -865,11 +864,10 @@ Fl_RGB_Image *Fl_X11_Screen_Driver::read_win_rectangle(int X, int Y, int w, int
   printf("map_entries      = %d\n", fl_visual->visual->map_entries);
 #endif // DEBUG
 
-  d = 3;
+  const int d = 3; // Depth of image
   uchar *p = NULL;
   // Allocate the image data array as needed...
-  const uchar *oldp = p;
-  if (!p) p = new uchar[w * h * d];
+  p = new uchar[w * h * d];
 
   // Initialize the default colors/alpha in the whole image...
   memset(p, 0, w * h * d);
@@ -1167,7 +1165,7 @@ Fl_RGB_Image *Fl_X11_Screen_Driver::read_win_rectangle(int X, int Y, int w, int
   XDestroyImage(image);
 
   Fl_RGB_Image *rgb = new Fl_RGB_Image(p, w, h, d);
-  if (!oldp) rgb->alloc_array = 1;
+  rgb->alloc_array = 1;
   return rgb;
 }