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WIN32 platform: Fix drag-n-drop to FLTK widget when the desktop is scaled and FLTK_HIDPI_SUPPORT is not defined.

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git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12308 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
This commit is contained in:
Manolo Gouy 2017-07-11 17:19:25 +00:00
parent b601e9558d
commit f84b9040f7
1 changed files with 15 additions and 1 deletions
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16
src/fl_dnd_win32.cxx
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@ -3,7 +3,7 @@
//
// Drag & Drop code for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2010 by Bill Spitzak and others.
// Copyright 1998-2017 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this
@ -84,6 +84,20 @@ public:
if( !pDataObj ) return E_INVALIDARG;
// set e_modifiers here from grfKeyState, set e_x and e_root_x
// check if FLTK handles this drag and return if it can't (i.e. BMP drag without filename)
/* Tricky point here: Not DPI–aware applications use different units for the 'POINTL pt' argument
of the DragEnter, DragOver, and Drop member functions.
DragEnter receives the mouse coordinates in unscaled screen units,
whereas DragOver and Drop receive the mouse coordinates in scaled units.
In the first case, dividing coordinates by DWM_scaling_factor() gives the scaled units used everywhere else.
DPI–aware applications transmit unscaled screen units to all 3 member functions.
These coordinates should be divided by the window's scale to get FLTK units.
*/
#ifndef FLTK_HIDPI_SUPPORT
float dwm_s = ((Fl_WinAPI_Screen_Driver*)Fl::screen_driver())->DWM_scaling_factor();
pt.x /= dwm_s;
pt.y /= dwm_s;
#endif
POINT ppt;
Fl::e_x_root = ppt.x = pt.x;
Fl::e_y_root = ppt.y = pt.y;