From 9315c26bb248157d0b37ef933e3d16779aed7dd9 Mon Sep 17 00:00:00 2001
From: Rodrigo Arias Mallo <rodarima@gmail.com>
Date: Sun, 13 Oct 2024 19:28:17 +0200
Subject: Repeat page scrolling when holding the button

When the page scroll mode is enabled, pressing and holding the scrollbar
will keep scrolling pages on that direction until the mouse button is
released.
---
 dw/fltkviewport.cc | 34 +++++++++++++++++++++++++++++-----
 dw/fltkviewport.hh |  6 ++++++
 dw/types.hh        |  2 +-
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/dw/fltkviewport.cc b/dw/fltkviewport.cc
index e9169495..fc9a0bed 100644
--- a/dw/fltkviewport.cc
+++ b/dw/fltkviewport.cc
@@ -74,6 +74,10 @@ FltkViewport::FltkViewport (int X, int Y, int W, int H, const char *label):
    horScrolling = verScrolling = dragScrolling = 0;
    scrollbarPageMode = false;
    pageOverlap = 50;
+   pageScrolling = core::NONE_CMD;
+
+   pageScrollDelay = 0.300;
+   pageScrollInterval = 0.100;
 
    gadgetOrientation[0] = GADGET_HORIZONTAL;
    gadgetOrientation[1] = GADGET_HORIZONTAL;
@@ -296,11 +300,19 @@ int FltkViewport::handle (int event)
    case FL_PUSH:
       if (vscrollbar->visible() && Fl::event_inside(vscrollbar)) {
          if (scrollbarPageMode ^ (bool) Fl::event_shift()) {
-            if (Fl::event_button() == FL_LEFT_MOUSE) {
-               scroll(core::SCREEN_DOWN_CMD);
-               return 1;
-            } else if (Fl::event_button() == FL_RIGHT_MOUSE) {
-               scroll(core::SCREEN_UP_CMD);
+            if (Fl::event_button() == FL_LEFT_MOUSE)
+               pageScrolling = core::SCREEN_DOWN_CMD;
+            else if (Fl::event_button() == FL_RIGHT_MOUSE)
+               pageScrolling = core::SCREEN_UP_CMD;
+            else
+               pageScrolling = core::NONE_CMD;
+
+            if (pageScrolling != core::NONE_CMD) {
+               scroll(pageScrolling);
+               /* Repeat until released */
+               if (!Fl::has_timeout(repeatPageScroll, this))
+                  Fl::add_timeout(pageScrollDelay, repeatPageScroll, this);
+
                return 1;
             }
          }
@@ -363,6 +375,7 @@ int FltkViewport::handle (int event)
       break;
 
    case FL_RELEASE:
+      Fl::remove_timeout(repeatPageScroll);
       Fl::remove_timeout(selectionScroll);
       if (Fl::event_button() == FL_MIDDLE_MOUSE) {
          setCursor (core::style::CURSOR_DEFAULT);
@@ -547,6 +560,17 @@ void FltkViewport::selectionScroll (void *data)
    Fl::repeat_timeout(0.025, selectionScroll, data);
 }
 
+void FltkViewport::repeatPageScroll ()
+{
+   scroll(pageScrolling);
+   Fl::repeat_timeout(pageScrollInterval, repeatPageScroll, this);
+}
+
+void FltkViewport::repeatPageScroll (void *data)
+{
+   ((FltkViewport *)data)->repeatPageScroll ();
+}
+
 void FltkViewport::setScrollbarOnLeft (bool enable)
 {
    scrollbarOnLeft = enable ? 1 : 0;
diff --git a/dw/fltkviewport.hh b/dw/fltkviewport.hh
index 2cff42d3..0948e2f2 100644
--- a/dw/fltkviewport.hh
+++ b/dw/fltkviewport.hh
@@ -46,6 +46,9 @@ private:
    int horScrolling, verScrolling;
    bool scrollbarPageMode;
    int pageOverlap;
+   enum dw::core::ScrollCommand pageScrolling;
+   float pageScrollInterval;
+   float pageScrollDelay;
 
    Fl_Scrollbar *vscrollbar, *hscrollbar;
 
@@ -65,6 +68,9 @@ private:
    void selectionScroll();
    static void selectionScroll(void *vport);
 
+   void repeatPageScroll ();
+   static void repeatPageScroll (void *data);
+
    void updateCanvasWidgets (int oldScrollX, int oldScrollY);
    static void draw_area (void *data, int x, int y, int w, int h);
 
diff --git a/dw/types.hh b/dw/types.hh
index 877593fe..eabf5ce7 100644
--- a/dw/types.hh
+++ b/dw/types.hh
@@ -34,7 +34,7 @@ enum VPosition
 
 enum ScrollCommand {SCREEN_UP_CMD, SCREEN_DOWN_CMD, SCREEN_LEFT_CMD,
                     SCREEN_RIGHT_CMD, LINE_UP_CMD, LINE_DOWN_CMD,
-                    LEFT_CMD, RIGHT_CMD, TOP_CMD, BOTTOM_CMD};
+                    LEFT_CMD, RIGHT_CMD, TOP_CMD, BOTTOM_CMD, NONE_CMD};
 
 /*
  * Different "layers" may be highlighted in a widget.
-- 
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