Revert "The debugging rectangles are not needed any more."

Still useful for debugging, particularly in combination with
gtktiledviewer.

This reverts commit dec025d4.

Change-Id: Id2174486c0427adf083be199ce2dbb453beb8f22
Reviewed-on: https://gerrit.libreoffice.org/63030
Tested-by: Jenkins
Reviewed-by: Jan Holesovsky <kendy@collabora.com>

desktop/source/lib/init.cxx

@@ -2152,6 +2152,19 @@ static void doc_paintTile(LibreOfficeKitDocument* pThis,
 
     pDoc->paintTile(*pDevice.get(), nCanvasWidth, nCanvasHeight,
                     nTilePosX, nTilePosY, nTileWidth, nTileHeight);
+
+    static bool bDebug = getenv("LOK_DEBUG_TILES") != nullptr;
+    if (bDebug)
+    {
+        // Draw a small red rectangle in the top left corner so that it's easy to see where a new tile begins.
+        tools::Rectangle aRect(0, 0, 5, 5);
+        aRect = pDevice->PixelToLogic(aRect);
+        pDevice->Push(PushFlags::FILLCOLOR | PushFlags::LINECOLOR);
+        pDevice->SetFillColor(COL_LIGHTRED);
+        pDevice->SetLineColor();
+        pDevice->DrawRect(aRect);
+        pDevice->Pop();
+    }
 #endif
 
 #else