commit 90c7e6bcb1fcd30f3230e51d2c057ffc3a48e796
Author:     ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
AuthorDate: Tue Dec 6 14:46:11 2022 +0100
Commit:     ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
CommitDate: Tue Dec 6 14:46:11 2022 +0100

    Fix issue #537 without damaging test/mandelbrot

 src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx
index eee3b0d..c054568 100644
--- src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx
+++ src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx
@@ -762,16 +762,21 @@ void Fl_Cairo_Graphics_Driver::draw_cached_pattern_(Fl_Image *img, cairo_pattern
   int Hs = Fl_Scalable_Graphics_Driver::floor(Y - cy + img->h(), s) - Ys;
   if (Ws == 0 || Hs == 0) return;
   cairo_save(cairo_);
-  cairo_rectangle(cairo_, X - 0.5, Y - 0.5, W + 0.5, H + 0.5);
-  cairo_clip(cairo_);
+  bool need_extend = (img->data_w() != Ws || img->data_h() != Hs || (W >= 2 && H >= 2));
+  if (need_extend || cx || cy || W < img->w() || H < img->h()) { // clip when necessary
+    cairo_rectangle(cairo_, X - 0.5, Y - 0.5, W + 0.5, H + 0.5);
+    cairo_clip(cairo_);
+  }
   // remove any scaling and the current "0.5" translation useful for lines but bad for images
   matrix.xx = matrix.yy = 1;
   matrix.x0 -= 0.5 * s; matrix.y0 -= 0.5 * s;
   cairo_set_matrix(cairo_, &matrix);
   if (img->d() >= 1) cairo_set_source(cairo_, pat);
-  cairo_pattern_set_filter(pat, Fl_RGB_Image::scaling_algorithm() == FL_RGB_SCALING_BILINEAR ?
+  if (need_extend) {
+    cairo_pattern_set_filter(pat, Fl_RGB_Image::scaling_algorithm() == FL_RGB_SCALING_BILINEAR ?
                            CAIRO_FILTER_GOOD : CAIRO_FILTER_FAST);
-  cairo_pattern_set_extend(pat, CAIRO_EXTEND_PAD);
+    cairo_pattern_set_extend(pat, CAIRO_EXTEND_PAD);
+  }
   cairo_matrix_init_scale(&matrix, double(img->data_w())/Ws, double(img->data_h())/Hs);
   cairo_matrix_translate(&matrix, -Xs , -Ys );
   cairo_pattern_set_matrix(pat, &matrix);