Fix #21039: Text rendering bleeds pixels through windows

Should fix [#21039 ](https://github.com/OpenRCT2/OpenRCT2/issues/21039).

As it is explained in the issue, the outline and inset code would not respect the DPI bounds in the drawing process by accessing e.g. `*(dst + 1)` to draw an outline, in this case to the right.
#### Approach
I approached this issue by creating a function `GetPixel()`  in `TTFSurface` that would return a value if the given x and y coordinates is a part of a TTF text, else 0. 

In the for loop, iterating through the TTF text, the if condition
```
if (surface->GetPixel(xx + srcX_start + 1, yy + srcY_start)
                        || surface->GetPixel(xx + srcX_start - 1, yy + srcY_start)
                        || surface->GetPixel(xx + srcX_start, yy + srcY_start + 1)
                        || surface->GetPixel(xx + srcX_start, yy + srcY_start - 1))
```
checks if the coordinates **(xx, yy)** is an outline of a text. the writing bounds. Adding `srcX_start`, which is 0 or `-skipX` if `skipX < 0`, when calling `GetPixel()`, would shift the pixel access to the correct position, where the text begins on the surface. The same is done for the Y axis. (Not having this would lead to the outlines/insets not moving with the text when the window with the TTF text moves)

distribution/changelog.txt

@@ -33,6 +33,7 @@
 - Fix: [#20628] Moving caret using Ctrl+left can move too far when using a multibyte grapheme.
 - Fix: [#20631] IME window not positioned correctly.
 - Fix: [#20845] Trying to save under a folder with no write permissions causes a crash.
+- Fix: [#21039] Text rendering bleeds pixels through windows.
 - Fix: [#21054] “No entrance” style is selected by default in the track designer.
 - Fix: [#21145] [Plugin] setInterval/setTimeout handle conflict.
 - Fix: [#21157] [Plugin] Widgets do not redraw correctly when updating disabled or visibility state. 

src/openrct2/drawing/Drawing.String.cpp

@@ -572,16 +572,20 @@ static void TTFDrawStringRawTTF(DrawPixelInfo& dpi, std::string_view text, TextD
     auto src = static_cast<const uint8_t*>(surface->pixels);
     uint8_t* dst = dpi.bits;
 
+    int32_t srcXStart = 0;
+    int32_t srcYStart = 0;
     if (skipX < 0)
     {
         width += skipX;
         src += -skipX;
+        srcXStart += -skipX;
         skipX = 0;
     }
     if (skipY < 0)
     {
         height += skipY;
         src += (-skipY * surface->pitch);
+        srcYStart += -skipY;
         skipY = 0;
     }
 
@@ -591,60 +595,44 @@ static void TTFDrawStringRawTTF(DrawPixelInfo& dpi, std::string_view text, TextD
     int32_t srcScanSkip = surface->pitch - width;
     int32_t dstScanSkip = dpi.width + dpi.pitch - width;
     uint8_t* dst_orig = dst;
-    const uint8_t* src_orig = src;
 
     // Draw shadow/outline
-    if (info->flags & TEXT_DRAW_FLAG_OUTLINE)
+    if (info->flags & (TEXT_DRAW_FLAG_OUTLINE | TEXT_DRAW_FLAG_INSET))
     {
-        for (int32_t yy = 0; yy < height - 0; yy++)
+        for (int32_t yy = 0; yy < height; yy++)
         {
-            for (int32_t xx = 0; xx < width - 0; xx++)
+            for (int32_t xx = 0; xx < width; xx++)
             {
-                if (*src != 0)
+                if (info->flags & TEXT_DRAW_FLAG_OUTLINE)
                 {
-                    // right
-                    if (xx + skipX < dpi.width + dpi.pitch - 1)
+                    if (GetPixel(*surface, xx + srcXStart + 1, yy + srcYStart)
+                        || GetPixel(*surface, xx + srcXStart - 1, yy + srcYStart)
+                        || GetPixel(*surface, xx + srcXStart, yy + srcYStart + 1)
+                        || GetPixel(*surface, xx + srcXStart, yy + srcYStart - 1))
                     {
-                        *(dst + 1) = info->palette[3];
-                    }
-                    // left
-                    if (xx + skipX > 1)
-                    {
-                        *(dst - 1) = info->palette[3];
-                    }
-                    // top
-                    if (yy + skipY > 1)
-                    {
-                        *(dst - width - dstScanSkip) = info->palette[3];
-                    }
-                    // bottom
-                    if (yy + skipY < dpi.height - 1)
-                    {
-                        *(dst + width + dstScanSkip) = info->palette[3];
+                        *dst = info->palette[3];
+                    }
+                }
+                if (info->flags & TEXT_DRAW_FLAG_INSET)
+                {
+                    if (GetPixel(*surface, xx + srcXStart - 1, yy + srcYStart - 1))
+                    {
+                        *dst = info->palette[3];
                     }
                 }
-                src++;
                 dst++;
             }
             // Skip any remaining bits
-            src += srcScanSkip;
             dst += dstScanSkip;
         }
     }
-
     dst = dst_orig;
-    src = src_orig;
     for (int32_t yy = 0; yy < height; yy++)
     {
         for (int32_t xx = 0; xx < width; xx++)
         {
             if (*src != 0)
             {
-                if (info->flags & TEXT_DRAW_FLAG_INSET)
-                {
-                    *(dst + width + dstScanSkip + 1) = info->palette[3];
-                }
-
                 if (*src > 180 || !use_hinting)
                 {
                     // Centre of the glyph: use full colour.

src/openrct2/drawing/TTF.cpp

@@ -374,6 +374,13 @@ void TTFFreeSurface(TTFSurface* surface)
     free(surface);
 }
 
+uint8_t GetPixel(const TTFSurface& surface, int32_t x, int32_t y)
+{
+    if (x < 0 || y < 0 || x >= surface.w || y >= surface.h)
+        return 0;
+    return static_cast<const uint8_t*>(surface.pixels)[y * surface.pitch + x];
+}
+
 #else
 
 #    include "TTF.h"

src/openrct2/drawing/TTF.h

@@ -43,5 +43,6 @@ void TTF_CloseFont(TTF_Font* font);
 void TTF_SetFontHinting(TTF_Font* font, int hinting);
 int TTF_GetFontHinting(const TTF_Font* font);
 void TTF_Quit(void);
+uint8_t GetPixel(const TTFSurface& surface, int32_t x, int32_t y);
 
 #endif // NO_TTF