From afba9f0de668c0b63fd94fbd62adb66485b9bc13 Mon Sep 17 00:00:00 2001
From: Harrison Lambeth <harrison@nau.edu>
Date: Sun, 12 Jan 2025 23:26:46 -0700
Subject: [PATCH] Add a function to reset text measurement cache (#181)

---
 README.md | 15 +++++++++++++++
 clay.h    | 16 ++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/README.md b/README.md
index e87cdf7..92580bf 100644
--- a/README.md
+++ b/README.md
@@ -173,9 +173,12 @@ For help starting out or to discuss clay, considering joining [the discord serve
     - [Clay_MinMemorySize](#clay_minmemorysize)
     - [Clay_CreateArenaWithCapacityAndMemory](#clay_createarenawithcapacityandmemory)
     - [Clay_SetMeasureTextFunction](#clay_setmeasuretextfunction)
+    - [Clay_ResetMeasureTextCache](#clau_resetmeasuretextcache)
     - [Clay_SetMaxElementCount](clay_setmaxelementcount)
     - [Clay_SetMaxMeasureTextCacheWordCount](#clay_setmaxmeasuretextcachewordcount)
     - [Clay_Initialize](#clay_initialize)
+    - [Clay_GetCurrentContext](#clay_getcurrentcontext)
+    - [Clay_SetCurrentContext](#clay_setcurrentcontext)
     - [Clay_SetLayoutDimensions](#clay_setlayoutdimensions)
     - [Clay_SetPointerState](#clay_setpointerstate)
     - [Clay_UpdateScrollContainers](#clay_updatescrollcontainers)
@@ -575,6 +578,14 @@ Takes a pointer to a function that can be used to measure the `width, height` di
 
 ---
 
+### Clay_ResetMeasureTextCache
+
+`void Clay_ResetMeasureTextCache(void)`
+
+Clay caches measurements from the provided MeasureTextFunction, and this will be sufficient for the majority of use-cases. However, if the measurements can depend on external factors that clay does not know about, like DPI changes, then the cached values may be incorrect. When one of these external factors changes, Clay_ResetMeasureTextCache can be called to force clay to recalculate all string measurements in the next frame.
+
+---
+
 ### Clay_SetMaxElementCount
 
 `void Clay_SetMaxElementCount(uint32_t maxElementCount)`
@@ -603,12 +614,16 @@ Initializes the internal memory mapping, sets the internal dimensions for layout
 
 Reference: [Clay_Arena](#clay_createarenawithcapacityandmemory), [Clay_ErrorHandler](#clay_errorhandler), [Clay_SetCurrentContext](#clay_setcurrentcontext)
 
+---
+
 ### Clay_SetCurrentContext
 
 `void Clay_SetCurrentContext(Clay_Context* context)`
 
 Sets the context that subsequent clay commands will operate on. You can get this reference from [Clay_Initialize](#clay_initialize) or [Clay_GetCurrentContext](#clay_getcurrentcontext). See [Running more than one Clay instance](#running-more-than-one-clay-instance).
 
+---
+
 ### Clay_GetCurrentContext
 
 `Clay_Context* Clay_GetCurrentContext()`
diff --git a/clay.h b/clay.h
index c489d36..0ccbc41 100644
--- a/clay.h
+++ b/clay.h
@@ -525,6 +525,7 @@ int32_t Clay_GetMaxElementCount(void);
 void Clay_SetMaxElementCount(int32_t maxElementCount);
 int32_t Clay_GetMaxMeasureTextCacheWordCount(void);
 void Clay_SetMaxMeasureTextCacheWordCount(int32_t maxMeasureTextCacheWordCount);
+void Clay_ResetMeasureTextCache(void);
 
 // Internal API functions required by macros
 void Clay__OpenElement(void);
@@ -4051,6 +4052,21 @@ void Clay_SetMaxMeasureTextCacheWordCount(int32_t maxMeasureTextCacheWordCount)
     }
 }
 
+CLAY_WASM_EXPORT("Clay_ResetMeasureTextCache")
+void Clay_ResetMeasureTextCache(void) {
+    Clay_Context* context = Clay_GetCurrentContext();
+    context->measureTextHashMapInternal.length = 0;
+    context->measureTextHashMapInternalFreeList.length = 0;
+    context->measureTextHashMap.length = 0;
+    context->measuredWords.length = 0;
+    context->measuredWordsFreeList.length = 0;
+    
+    for (int32_t i = 0; i < context->measureTextHashMap.capacity; ++i) {
+        context->measureTextHashMap.internalArray[i] = 0;
+    }
+    context->measureTextHashMapInternal.length = 1; // Reserve the 0 value to mean "no next element"
+}
+
 #endif // CLAY_IMPLEMENTATION
 
 /*