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[STR Active]

Link: https://www.fltk.org/str.php?L3521
Version: 1.4-feature


Please see attached file
'0001-Switch-hor.-vert.-scrolling-with-SHIFT-STR-3521.patch' for a proof of
concept. Please apply with `git am' (hint: after creating a feature branch)
or `patch -p1' for testing.

This patch does *unconditionally* change scrollbar behavior by exchanging
horizontal and vertical mousewheel movement values (Fl::event_dx and
Fl::event_dy) if the Shift key is pressed during mousewheel movement.

As said above this *may* break existing programs that don't care about
shift key state when interpreting mousewheel events.

I don't know if these concerns are critical though. If yes, I suggest to
use a global flag for the entire program that can /disable/ the new feature
as opposed to a per-scrollbar flag.

Note that the patch is local in Fl_Scrollbar mousewheel event handling
since this had already the distinction of horizontal and vertical
scrollbars.


Link: https://www.fltk.org/str.php?L3521
Version: 1.4-feature

From d5b0ba2a17ab277f0e9f074ae243642e8577cdfb Mon Sep 17 00:00:00 2001
From: Albrecht Schlosser <albrechts.fltk@online.de>
Date: Fri, 17 May 2019 14:23:37 +0200
Subject: [PATCH] Switch hor./vert. scrolling with SHIFT (STR 3521)

This is only a proof of concept. The new scrolling feature simply
exchanges horizontal and vertical mousewheel movement if the
Shift key is pressed while the mousewheel is used.

This *may* break existing programs that don't care about Shift key
state, but it's a local, simple and efficient solution.
---
 src/Fl_Scrollbar.cxx | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/Fl_Scrollbar.cxx b/src/Fl_Scrollbar.cxx
index a659e8e14..eab29f086 100644
--- a/src/Fl_Scrollbar.cxx
+++ b/src/Fl_Scrollbar.cxx
@@ -104,6 +104,7 @@ int Fl_Scrollbar::handle(int event) {
     else area = 8;
   }
 
+  int e_dx = 0, e_dy = 0;  // used in FL_MOUSEWHEEL event handling
   switch (event) {
   case FL_ENTER:
   case FL_LEAVE:
@@ -131,15 +132,22 @@ int Fl_Scrollbar::handle(int event) {
     if (pushed_) return 1;
     return Fl_Slider::handle(event, X,Y,W,H);
   case FL_MOUSEWHEEL :
+    if (Fl::event_state() & FL_SHIFT) { // shift key was down during mousewheel event
+      e_dx = Fl::e_dy; // flip mousewheel movement (horizontal/vertical)
+      e_dy = Fl::e_dx;
+    } else {
+      e_dx = Fl::e_dx; // normal mousewheel movement
+      e_dy = Fl::e_dy;
+    }
     if (horizontal()) {
-      if (Fl::e_dx==0) return 0;
+      if (e_dx == 0) return 0;
       int ls = maximum()>=minimum() ? linesize_ : -linesize_;
-      handle_drag(clamp(value() + ls * Fl::e_dx));
+      handle_drag(clamp(value() + ls * e_dx));
       return 1;
     } else {
-      if (Fl::e_dy==0) return 0;
+      if (e_dy == 0) return 0;
       int ls = maximum()>=minimum() ? linesize_ : -linesize_;
-      handle_drag(clamp(value() + ls * Fl::e_dy));
+      handle_drag(clamp(value() + ls * e_dy));
       return 1;
     }
   case FL_SHORTCUT:
-- 
2.17.1