Fix "Xrender blurs adjacent images with bilinear scaling" (#633)

Many thanks to @wcout for providing this fix.

Xrender now draws images in the same way when tiling images
or not when FL_RGB_SCALING_BILINEAR is on.
This allows to remove static bool Fl_Tiled_Image::drawing_tiled_image()
which becomes unused.

FL/Fl_Tiled_Image.H

@@ -30,16 +30,12 @@
   color_average(), desaturate(), or inactive() methods.
 */
 class FL_EXPORT Fl_Tiled_Image : public Fl_Image {
-private:
-  static bool drawing_tiled_image_;
 protected:
 
   Fl_Image      *image_;                // The image that is tiled
   int           alloc_image_;           // Did we allocate this image?
 
 public:
-  /** Returns true when the FLTK library is currently drawing an Fl_Tiled_Image object. */
-  static inline bool drawing_tiled_image() { return drawing_tiled_image_;};
   Fl_Tiled_Image(Fl_Image *i, int W = 0, int H = 0);
   virtual ~Fl_Tiled_Image();
 

src/Fl_Tiled_Image.cxx

@@ -20,8 +20,6 @@
 #include <FL/Fl_Window.H>
 #include <FL/fl_draw.H>
 
-bool Fl_Tiled_Image::drawing_tiled_image_ = false;
-
 /**
   The constructors create a new tiled image containing the specified image.
   Use a width and height of 0 to tile the whole window/widget.
@@ -183,7 +181,6 @@ Fl_Tiled_Image::draw(int X,     // I - Starting X position
   if (W == 0 || H == 0) return;
 
   fl_push_clip(X, Y, W, H);
-  drawing_tiled_image_ = true;
 
   if (cx > 0) iw -= cx;         // crop image
   if (cy > 0) ih -= cy;
@@ -197,6 +194,5 @@ Fl_Tiled_Image::draw(int X,     // I - Starting X position
       }
     }
   }
-  drawing_tiled_image_ = false;
   fl_pop_clip();
 }

src/drivers/Xlib/Fl_Xlib_Graphics_Driver_image.cxx

@@ -56,8 +56,11 @@
 #  include "../../Fl_XColor.H"
 #  include "../../flstring.h"
 #if HAVE_XRENDER
-#include <X11/extensions/Xrender.h>
-#endif
+#  include <X11/extensions/Xrender.h>
+#  if RENDER_MAJOR * 100 + RENDER_MAJOR < 10
+#    define RepeatPad  2
+#  endif
+#endif // HAVE_XRENDER
 
 static XImage xi;       // template used to pass info to X
 static int bytes_per_pixel;
@@ -806,8 +809,10 @@ int Fl_Xlib_Graphics_Driver::scale_and_render_pixmap(Fl_Offscreen pixmap, int de
   static XRenderPictFormat *fmt24 = XRenderFindStandardFormat(fl_display, PictStandardRGB24);
   static XRenderPictFormat *fmt32 = XRenderFindStandardFormat(fl_display, PictStandardARGB32);
   static XRenderPictFormat *dstfmt = XRenderFindVisualFormat(fl_display, fl_visual->visual);
-  Picture src = XRenderCreatePicture(fl_display, (Pixmap)pixmap, has_alpha ?fmt32:fmt24, 0, &srcattr);
-  Picture dst = XRenderCreatePicture(fl_display, fl_window, dstfmt, 0, &srcattr);
+  srcattr.repeat = RepeatPad;
+  Picture src = XRenderCreatePicture(fl_display, (Pixmap)pixmap, has_alpha ?fmt32:fmt24,
+                                     CPRepeat, &srcattr);
+  Picture dst = XRenderCreatePicture(fl_display, fl_window, dstfmt, 0, 0);
   if (!src || !dst) {
     fprintf(stderr, "Failed to create Render pictures (%lu %lu)\n", src, dst);
     return 0;
@@ -824,10 +829,7 @@ int Fl_Xlib_Graphics_Driver::scale_and_render_pixmap(Fl_Offscreen pixmap, int de
       { XDoubleToFixed( 0 ),       XDoubleToFixed( 0 ),       XDoubleToFixed( 1 ) }
     }};
     XRenderSetPictureTransform(fl_display, src, &mat);
-    if (Fl_Image::scaling_algorithm() == FL_RGB_SCALING_BILINEAR &&
-          !Fl_Tiled_Image::drawing_tiled_image()) {
-      // The filter is not used when drawing tiled images because drawn image edges
-      // become somewhat blurry.
+    if (Fl_Image::scaling_algorithm() == FL_RGB_SCALING_BILINEAR) {
       XRenderSetPictureFilter(fl_display, src, FilterBilinear, 0, 0);
       // A note at  https://www.talisman.org/~erlkonig/misc/x11-composite-tutorial/ :
       // "When you use a filter you'll probably want to use PictOpOver as the render op,