[PATCH v3 0/1] MR8178: user32: Fix the number of characters processed by DrawTextExW.

[JiangYi Chen (＠meshine)]

uiLengthDrawn should represent the number of characters that have been processed.
However, the original implementation uses len (the count of displayed characters
in the current line), which is not accurate.
When text requires line breaks or special processing (such as adding an ellipsis),
the actual number of processed characters may differ from the number of displayed
characters.
When the DT_CALCRECT flag is absent, len gets decremented to 0 during the drawing loop.
Consequently, uiLengthDrawn becomes inaccurate since it relies on len's value for statistics.

@zhiyi @julliard 

Signed-off-by: chenjiangyi <chenjiangyi(a)uniontech.com>

--
  v3: user32: Fix the number of characters processed by DrawTextExW.
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/8178

[PATCH v3 1/1] user32: Fix the number of characters processed by DrawTextExW.

[chenjiangyi]

From: chenjiangyi <chenjiangyi(a)uniontech.com>

uiLengthDrawn should represent the number of characters that have been processed.
However, the original implementation uses len (the count of displayed characters
in the current line), which is not accurate.

When text requires line breaks or special processing (such as adding an ellipsis),
the actual number of processed characters may differ from the number of displayed
characters.

When the DT_CALCRECT flag is absent, len gets decremented to 0 during the drawing loop.

Consequently, uiLengthDrawn becomes inaccurate since it relies on len's value for statistics.
---
 dlls/user32/tests/text.c | 29 +++++++++++++++++++++++++++++
 dlls/user32/text.c       |  8 +++++---
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/dlls/user32/tests/text.c b/dlls/user32/tests/text.c
index d3228eae1e0..71c04382cf7 100644
--- a/dlls/user32/tests/text.c
+++ b/dlls/user32/tests/text.c
@@ -656,6 +656,35 @@ static void test_DrawTextCalcRect(void)
     ok(rect.top == rect2.top, "unexpected value %ld, got %ld\n", rect.top, rect2.top);
     ok(rect.bottom == rect2.bottom , "unexpected value %ld, got %ld\n", rect.bottom, rect2.bottom);
 
+    /* Test uiLengthDrawn calculation */
+    SelectObject(hdc, hOldFont);
+    ret = DeleteObject(hFont);
+    ok(ret, "DeleteObject error %lu\n", GetLastError());
+    lf.lfHeight = 200 * 9 / 72;
+    hFont = CreateFontIndirectA(&lf);
+    ok(hFont != 0, "CreateFontIndirectA error %lu\n", GetLastError());
+    hOldFont = SelectObject(hdc, hFont);
+
+    SetRect(&rect, 0, 0, 100, 25);
+    memset(&dtp, 0, sizeof(dtp));
+    dtp.cbSize = sizeof(dtp);
+    textheight = DrawTextExW(hdc, textW, lstrlenW(textW), &rect, DT_EDITCONTROL | DT_NOPREFIX | DT_WORDBREAK, &dtp);
+    ok(dtp.uiLengthDrawn == 10, "Unexpected uiLengthDrawn %d\n", dtp.uiLengthDrawn );
+
+    memset(&dtp, 0, sizeof(dtp));
+    dtp.cbSize = sizeof(dtp);
+    textheight = DrawTextExW(hdc, textW, lstrlenW(textW), &rect, DT_EDITCONTROL | DT_NOPREFIX | DT_WORDBREAK | DT_CALCRECT, &dtp);
+    ok(dtp.uiLengthDrawn == 16, "Unexpected uiLengthDrawn %d\n", dtp.uiLengthDrawn );
+
+    memset(&dtp, 0, sizeof(dtp));
+    dtp.cbSize = sizeof(dtp);
+    textheight = DrawTextExW(hdc, (LPWSTR)L"a 1\tb2c3", lstrlenW(L"a 1\tb2c3"), &rect, DT_EDITCONTROL | DT_NOPREFIX | DT_WORDBREAK, &dtp);
+    ok(dtp.uiLengthDrawn == 8, "Unexpected uiLengthDrawn %d\n", dtp.uiLengthDrawn );
+
+    memset(&dtp, 0, sizeof(dtp));
+    dtp.cbSize = sizeof(dtp);
+    textheight = DrawTextExW(hdc, (LPWSTR)L"a 1\tb2c3", lstrlenW(L"a 1\tb2c3"), &rect, DT_EDITCONTROL | DT_NOPREFIX | DT_WORDBREAK | DT_CALCRECT, &dtp);
+    ok(dtp.uiLengthDrawn == 8, "Unexpected uiLengthDrawn %d\n", dtp.uiLengthDrawn );
 
     SelectObject(hdc, hOldFont);
     ret = DeleteObject(hFont);
diff --git a/dlls/user32/text.c b/dlls/user32/text.c
index 1896627c893..c8ca0903b8c 100644
--- a/dlls/user32/text.c
+++ b/dlls/user32/text.c
@@ -871,7 +871,7 @@ INT WINAPI DrawTextExW( HDC hdc, LPWSTR str, INT i_count,
     WCHAR *retstr;
     size_t size_retstr;
     WCHAR line[MAX_BUFFER];
-    int len, lh, count=i_count;
+    int len, lh, old_count, count=i_count;
     TEXTMETRICW tm;
     int lmargin = 0, rmargin = 0;
     int x, y, width;
@@ -978,7 +978,11 @@ INT WINAPI DrawTextExW( HDC hdc, LPWSTR str, INT i_count,
             last_line = !(flags & DT_NOCLIP) && y - ((flags & DT_EDITCONTROL) ? 2*lh-1 : lh) < rect->bottom;
 	else
             last_line = !(flags & DT_NOCLIP) && y + ((flags & DT_EDITCONTROL) ? 2*lh-1 : lh) > rect->bottom;
+
+    old_count = count;
 	strPtr = TEXT_NextLineW(hdc, strPtr, &count, line, &len, width, flags, &size, last_line, retstr, tabwidth, &prefix_offset, &ellip);
+    if (dtp)
+        dtp->uiLengthDrawn += old_count - count;
 
         if (flags & DT_CENTER)
             x = (rect->left + lmargin + rect->right - rmargin - size.cx) / 2;
@@ -1051,8 +1055,6 @@ INT WINAPI DrawTextExW( HDC hdc, LPWSTR str, INT i_count,
 	    y -= lh;
         else
 	    y += lh;
-        if (dtp)
-            dtp->uiLengthDrawn += len;
     }
     while (strPtr && !last_line);
 
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/8178