Add fl_remove_scale()/fl_restore_scale() to transiently draw without scaling factor.

This new API is a response to this message in fltk.general :
Can custom box type functions handle their own high-DPI screen scaling?

1 files changed, 17 insertions, 0 deletions

diff --git a/src/fl_draw.cxx b/src/fl_draw.cxx
index 72a117df0..538e63f2a 100644
--- a/src/fl_draw.cxx
+++ b/src/fl_draw.cxx
@@ -458,3 +458,20 @@ int fl_height(int font, int size) {
     fl_font(tf,ts);                       // restore
     return(height);
 }
+
+/** Removes any GUI scaling factor in subsequent drawing operations.
+ This must be matched by a later call to fl_restore_scale().
+ This function can be used to transiently perform drawing operations
+ that are not rescaled by the current value of the GUI scaling factor.
+ The resulting drawing context has no clipping region.
+ \return The GUI scaling factor value that was applied when the function started.
+ */
+float fl_remove_scale() {
+  return fl_graphics_driver->remove_scale();
+}
+
+/** Restores the GUI scaling factor and the clipping region in subsequent drawing operations.
+ \param s Value returned by a previous call to fl_remove_scale(). */
+void fl_restore_scale(float s) {
+  fl_graphics_driver->restore_scale(s);
+}