From 0f92e50ce86f2aa96a79b46f6099acde713e1944 Mon Sep 17 00:00:00 2001
From: Marc Durdin <marc@durdin.net>
Date: Wed, 23 Jun 2021 19:32:05 +1000
Subject: [PATCH] fix(windows): osk scaling mismatch on horz axis

Font scaling on individual keys would ignore the vertical axis if the
horizontal axis reached the key width threshold, rather than calculating
the minimum of the two axes. This lead to weird effects, such as adding
characters to a key could make the font larger rather than smaller!

Reported by @jmdurdin.
---
 .../global/delphi/comp/OnScreenKeyboard.pas   | 45 ++++++++++++-------
 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/windows/src/global/delphi/comp/OnScreenKeyboard.pas b/windows/src/global/delphi/comp/OnScreenKeyboard.pas
index f045d39e39..1a48b0d051 100644
--- a/windows/src/global/delphi/comp/OnScreenKeyboard.pas
+++ b/windows/src/global/delphi/comp/OnScreenKeyboard.pas
@@ -1,18 +1,18 @@
 (*
   Name:             OnScreenKeyboard
   Copyright:        Copyright (C) SIL International.
-  Documentation:    
-  Description:      
+  Documentation:
+  Description:
   Create Date:      23 Aug 2006
 
   Modified Date:    24 Jul 2015
   Authors:          mcdurdin
-  Related Files:    
-  Dependencies:     
+  Related Files:
+  Dependencies:
 
-  Bugs:             
-  Todo:             
-  Notes:            
+  Bugs:
+  Todo:
+  Notes:
   History:          23 Aug 2006 - mcdurdin - Initial version
                     30 Aug 2006 - mcdurdin - Fix underlying layout published bug
                     14 Sep 2006 - mcdurdin - Add Transparent flag, retrieve aspected size, polish drawing
@@ -264,6 +264,8 @@ const   // I4098   // I4799
 implementation
 
 uses
+  System.Math,
+
   Glossary,
   ScanCodeMap,
   Types,
@@ -379,7 +381,7 @@ begin
   ParentBackground := True;
 
   UpdateEuroLayout;  // I764
-  
+
   if HasParent then // I1227, I904, I1102 - crash export OSK to BMP, PNG
     CalcKeyFontSizes;
 end;
@@ -730,7 +732,7 @@ begin
     begin
       k2 := FHoverKey;
       if Assigned(k) and not k.Enabled then k := nil;
-      
+
       FHoverKey := k;
       DoDrawKey(Canvas, k); //InvalidateKey(k);
       DoDrawKey(Canvas, k2); //InvalidateKey(k2);
@@ -1383,16 +1385,27 @@ var
 
         if GetTextExtentPoint32W(Canvas.Handle, PWideChar(FKeyValue), Length(FKeyValue), FTextExtent) then  // I2576
         begin
-          if FTextExtent.cx > (RText.Right - RText.Left) * FKeyboard.FScale then
+          if (FTextExtent.cx > (RText.Right - RText.Left) * FKeyboard.FScale) or
+            (FTextExtent.cy > (RText.Bottom - RText.Top) * FKeyboard.FScale) then
           begin
-            Font.Height := Trunc(Font.Height * (RText.Right - RText.Left) * FKeyboard.FScale / FTextExtent.cx);
-          end
-          else if FTextExtent.cy > (RText.Bottom - RText.Top) * FKeyboard.FScale then
-          begin
-            Font.Height := Trunc(Font.Height * (RText.Bottom - RText.Top) * FKeyboard.FScale / FTextExtent.cy);
-          end
+            // font.height may be either positive or negative, depending on whether
+            // internal leading is included. It doesn't matter, so long as we keep
+            // the same factor.
+            if Font.Height < 0 then
+              Font.Height := System.Math.Max(
+                Trunc(Font.Height * (RText.Right - RText.Left) * FKeyboard.FScale / FTextExtent.cx),
+                Trunc(Font.Height * (RText.Bottom - RText.Top) * FKeyboard.FScale / FTextExtent.cy)
+              )
+            else
+              Font.Height := System.Math.Min(
+                Trunc(Font.Height * (RText.Right - RText.Left) * FKeyboard.FScale / FTextExtent.cx),
+                Trunc(Font.Height * (RText.Bottom - RText.Top) * FKeyboard.FScale / FTextExtent.cy)
+              );
+          end;
         end;
 
+        // TODO: in future re-scale the font here per designer's preference
+        //       but this requires a file format change, so a much bigger scope
 
         if not Enabled then      Font.Color := $808080
         else                     Font.Color := clWindowText;