From 89449280dc6be1d0d54359d48fc74d6c05f0c0c0 Mon Sep 17 00:00:00 2001
From: ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
Date: Thu, 26 Mar 2020 06:29:25 +0100
Subject: Doc: more details about initialisation of display scale factors.

---
 documentation/src/osissues.dox | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'documentation/src/osissues.dox')

diff --git a/documentation/src/osissues.dox b/documentation/src/osissues.dox
index c391d28c0..d70118d69 100644
--- a/documentation/src/osissues.dox
+++ b/documentation/src/osissues.dox
@@ -474,6 +474,12 @@ the class "fltk" is used (e.g. <tt>fltk.background</tt>). If no
 match is found, a global search is done (e.g.
 <tt>*background</tt>).
 
+\subsection osissues_x_scaling Dislay Scaling Factor
+
+FLTK uses the value of the Xft.dpi resource divided by 96.
+to initialize the display scaling factor. That is also
+what is done by the gnome and KDE desktops.
+
 \section osissues_win32 The Windows Interface
 
 The Windows interface provides access to the Windows GDI
@@ -577,6 +583,14 @@ DrawSomething(fl_gc, ..., fl_brush());
 It may also be useful to refer to Fl_Window::current()
 to get the window's size or position.
 
+\subsection osissues_windows_scaling Dislay Scaling Factor
+
+FLTK uses the value given by function GetDpiForMonitor() divided by 96.
+to initialize the scaling factor of each display in the system.
+This matches the value of
+"Change the size of text, apps and other items" found in section
+"System" subsection "Display" of Windows settings.
+
 \subsection osissues_icon_windows Setting the Icon of a Window
 
 FLTK currently supports setting a window's icon *before* it
-- 
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