Zhiyi Zhang : win32u: Choose a smaller ppem to avoid exceeding the requested font height.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 58b477d1581f715d75c2e117ffa9489c6e64a678
URL:    https://gitlab.winehq.org/wine/wine/-/commit/58b477d1581f715d75c2e117ffa9489...

Author: Zhiyi Zhang <zzhang(a)codeweavers.com>
Date:   Fri Aug 12 11:32:54 2022 +0800

win32u: Choose a smaller ppem to avoid exceeding the requested font height.

When height > 0, CreateFontA/W() should not return a font face exceeding the requested height.
For instance, Tahoma has 2049 units of ascent, 423 units of descent and its units per EM square is
2048. When requesting a font 20 pixels in height, ppem = units_per_EM * requested_height / (ascent + descent)
= 2048 * 20 / (2049 + 423) = 16.57 ~= 17. When getting the resulting height back from the ppem,
resulting_height = (ascent + descent) * ppem / units_per_EM = (2049.0 + 423) * 17 / 2048 = 20.52
~=21. So it ends up getting a larger font than requested and violates the spec.

Fix Nancy Drew: Legend of the Crystal Skull crash at start.

Signed-off-by: Zhiyi Zhang <zzhang(a)codeweavers.com>

---

 dlls/gdi32/tests/font.c |  1 -
 dlls/win32u/freetype.c  | 12 ++++++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/dlls/gdi32/tests/font.c b/dlls/gdi32/tests/font.c
index b7624942ead..12a5bff5969 100644
--- a/dlls/gdi32/tests/font.c
+++ b/dlls/gdi32/tests/font.c
@@ -4124,7 +4124,6 @@ static void test_GetTextMetrics(void)
     old_hf = SelectObject(hdc, hf);
     ret = GetTextMetricsA(hdc, &tm);
     ok(ret, "GetTextMetricsA failed, error %lu\n", GetLastError());
-    todo_wine
     ok(tm.tmHeight <= 20, "Got unexpected tmHeight %ld\n", tm.tmHeight);
     SelectObject(hdc, old_hf);
     DeleteObject(hf);
diff --git a/dlls/win32u/freetype.c b/dlls/win32u/freetype.c
index f6cdddd7819..d911039647b 100644
--- a/dlls/win32u/freetype.c
+++ b/dlls/win32u/freetype.c
@@ -1927,10 +1927,18 @@ static LONG calc_ppem_for_height(FT_Face ft_face, LONG height)
 
     if(height > 0) {
         USHORT windescent = get_fixed_windescent(pOS2->usWinDescent);
+        LONG units;
+
         if(pOS2->usWinAscent + windescent == 0)
-            ppem = pFT_MulDiv(ft_face->units_per_EM, height, pHori->Ascender - pHori->Descender);
+            units = pHori->Ascender - pHori->Descender;
         else
-            ppem = pFT_MulDiv(ft_face->units_per_EM, height, pOS2->usWinAscent + windescent);
+            units = pOS2->usWinAscent + windescent;
+        ppem = pFT_MulDiv(ft_face->units_per_EM, height, units);
+
+        /* If rounding ends up getting a font exceeding height, choose a smaller ppem */
+        if(ppem > 1 && pFT_MulDiv(units, ppem, ft_face->units_per_EM) > height)
+            --ppem;
+
         if(ppem > MAX_PPEM) {
             WARN("Ignoring too large height %d, ppem %d\n", height, ppem);
             ppem = 1;