Use memory pool for PolyTextOut items in GDI Renderer (#8619)

Converts the poly text out string and width buffers to use a memory pool since we free/alloc those every frame and are just going to reuse them over and over. 

## PR Checklist
* [x] Supports #3075
* [x] I work here.
* [x] Profiled memory before/after. Tested manually with `big.txt`.

## Detailed Description of the Pull Request / Additional comments
- Sets up a PMR memory pool for the GDI Engine. It tends to alloc and free a bunch of little buffers during painting frames. The pool will likely hold onto that memory frame over frame, but we'd just be using it again and again and again anyway. So this way we avoid all the system memory allocator locks and syscalls.

## Validation Steps Performed
- Ran `big.txt` about 10x in the window. Checked WPR/WPA profile output before/after.

.github/actions/spell-check/dictionary/apis.txt

@@ -56,6 +56,7 @@ otms
 OUTLINETEXTMETRICW
 overridable
 PAGESCROLL
+pmr
 RETURNCMD
 rfind
 roundf

src/inc/LibraryIncludes.h

@@ -23,6 +23,7 @@
 #include <deque>
 #include <list>
 #include <memory>
+#include <memory_resource>
 #include <map>
 #include <mutex>
 #include <shared_mutex>

src/renderer/gdi/gdirenderer.hpp

@@ -125,6 +125,13 @@ namespace Microsoft::Console::Render
         COLORREF _lastBg;
         bool _lastFontItalic;
 
+        // Memory pooling to save alloc/free work to the OS for things
+        // frequently created and dropped.
+        // It's important the pool is first so it can be given to the others on construction.
+        std::pmr::unsynchronized_pool_resource _pool;
+        std::pmr::vector<std::pmr::wstring> _polyStrings;
+        std::pmr::vector<std::pmr::basic_string<int>> _polyWidths;
+
         [[nodiscard]] HRESULT _InvalidCombine(const RECT* const prc) noexcept;
         [[nodiscard]] HRESULT _InvalidOffset(const POINT* const ppt) noexcept;
         [[nodiscard]] HRESULT _InvalidRestrict() noexcept;

src/renderer/gdi/paint.cpp

@@ -308,13 +308,11 @@ using namespace Microsoft::Console::Render;
 
         const auto pPolyTextLine = &_pPolyText[_cPolyText];
 
-        auto pwsPoly = std::make_unique<wchar_t[]>(cchLine);
-        RETURN_IF_NULL_ALLOC(pwsPoly);
+        auto& polyString = _polyStrings.emplace_back(cchLine, UNICODE_NULL);
 
         COORD const coordFontSize = _GetFontSize();
 
-        auto rgdxPoly = std::make_unique<int[]>(cchLine);
-        RETURN_IF_NULL_ALLOC(rgdxPoly);
+        auto& polyWidth = _polyWidths.emplace_back(cchLine, 0);
 
         // Sum up the total widths the entire line/run is expected to take while
         // copying the pixel widths into a structure to direct GDI how many pixels to use per character.
@@ -327,9 +325,9 @@ using namespace Microsoft::Console::Render;
 
             // Our GDI renderer hasn't and isn't going to handle things above U+FFFF or sequences.
             // So replace anything complicated with a replacement character for drawing purposes.
-            pwsPoly[i] = cluster.GetTextAsSingle();
-            rgdxPoly[i] = gsl::narrow<int>(cluster.GetColumns()) * coordFontSize.X;
-            cchCharWidths += rgdxPoly[i];
+            polyString[i] = cluster.GetTextAsSingle();
+            polyWidth[i] = gsl::narrow<int>(cluster.GetColumns()) * coordFontSize.X;
+            cchCharWidths += polyWidth[i];
         }
 
         // Detect and convert for raster font...
@@ -338,7 +336,7 @@ using namespace Microsoft::Console::Render;
             // dispatch conversion into our codepage
 
             // Find out the bytes required
-            int const cbRequired = WideCharToMultiByte(_fontCodepage, 0, pwsPoly.get(), (int)cchLine, nullptr, 0, nullptr, nullptr);
+            int const cbRequired = WideCharToMultiByte(_fontCodepage, 0, polyString.data(), (int)cchLine, nullptr, 0, nullptr, nullptr);
 
             if (cbRequired != 0)
             {
@@ -346,7 +344,7 @@ using namespace Microsoft::Console::Render;
                 auto psConverted = std::make_unique<char[]>(cbRequired);
 
                 // Attempt conversion to current codepage
-                int const cbConverted = WideCharToMultiByte(_fontCodepage, 0, pwsPoly.get(), (int)cchLine, psConverted.get(), cbRequired, nullptr, nullptr);
+                int const cbConverted = WideCharToMultiByte(_fontCodepage, 0, polyString.data(), (int)cchLine, psConverted.get(), cbRequired, nullptr, nullptr);
 
                 // If successful...
                 if (cbConverted != 0)
@@ -356,22 +354,22 @@ using namespace Microsoft::Console::Render;
 
                     if (cchRequired != 0)
                     {
-                        auto pwsConvert = std::make_unique<wchar_t[]>(cchRequired);
+                        std::pmr::wstring polyConvert(cchRequired, UNICODE_NULL, &_pool);
 
                         // Then do the actual conversion.
-                        int const cchConverted = MultiByteToWideChar(CP_ACP, 0, psConverted.get(), cbRequired, pwsConvert.get(), cchRequired);
+                        int const cchConverted = MultiByteToWideChar(CP_ACP, 0, psConverted.get(), cbRequired, polyConvert.data(), cchRequired);
 
                         if (cchConverted != 0)
                         {
                             // If all successful, use this instead.
-                            pwsPoly.swap(pwsConvert);
+                            polyString.swap(polyConvert);
                         }
                     }
                 }
             }
         }
 
-        pPolyTextLine->lpstr = pwsPoly.release();
+        pPolyTextLine->lpstr = polyString.data();
         pPolyTextLine->n = gsl::narrow<UINT>(clusters.size());
         pPolyTextLine->x = ptDraw.x;
         pPolyTextLine->y = ptDraw.y;
@@ -380,7 +378,7 @@ using namespace Microsoft::Console::Render;
         pPolyTextLine->rcl.top = pPolyTextLine->y;
         pPolyTextLine->rcl.right = pPolyTextLine->rcl.left + ((SHORT)cchCharWidths * coordFontSize.X);
         pPolyTextLine->rcl.bottom = pPolyTextLine->rcl.top + coordFontSize.Y;
-        pPolyTextLine->pdx = rgdxPoly.release();
+        pPolyTextLine->pdx = polyWidth.data();
 
         if (trimLeft)
         {
@@ -417,20 +415,10 @@ using namespace Microsoft::Console::Render;
             hr = E_FAIL;
         }
 
-        for (size_t iPoly = 0; iPoly < _cPolyText; iPoly++)
-        {
-            if (nullptr != _pPolyText[iPoly].lpstr)
-            {
-                delete[] _pPolyText[iPoly].lpstr;
-                _pPolyText[iPoly].lpstr = nullptr;
-            }
+        _polyStrings.clear();
+        _polyWidths.clear();
 
-            if (nullptr != _pPolyText[iPoly].pdx)
-            {
-                delete[] _pPolyText[iPoly].pdx;
-                _pPolyText[iPoly].pdx = nullptr;
-            }
-        }
+        ZeroMemory(_pPolyText, sizeof(_pPolyText));
 
         _cPolyText = 0;
     }

src/renderer/gdi/state.cpp

@@ -32,7 +32,10 @@ GdiEngine::GdiEngine() :
     _lastFontItalic(false),
     _fPaintStarted(false),
     _hfont(nullptr),
-    _hfontItalic(nullptr)
+    _hfontItalic(nullptr),
+    _pool{}, // It's important the pool is first so it can be given to the others on construction.
+    _polyStrings{ &_pool },
+    _polyWidths{ &_pool }
 {
     ZeroMemory(_pPolyText, sizeof(POLYTEXTW) * s_cPolyTextCache);
     _rcInvalid = { 0 };