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@codeweavers.com>

win32u: Choose a smaller ppem to avoid exceeding the requested font height.
58b477d1 · Zhiyi Zhang · Alexandre Julliard · 821b36e0 · 58b477d1 · 58b477d1
Commit 58b477d1 authored Aug 12, 2022 by Zhiyi Zhang Committed by Alexandre Julliard Aug 19, 2022
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font.c dlls/gdi32/tests/font.c +0 -1

freetype.c dlls/win32u/freetype.c +10 -2

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--- 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);

--- 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;