TextUnformatted: Using memchr(), fixed not properly testing for text_end bound + comments.

Internals: Added ImStreolRange() + used in LogRenderedText() + comments.

docs/CHANGELOG.txt

@@ -56,6 +56,8 @@ Other Changes:
 - BeginChild(): Fixed BeginChild(const char*, ...) variation erroneously not applying the ID stack
   to the provided string to uniquely identify the child window. This was undoing an intentional change
   introduced in 1.50 and broken in 1.60. (#1698, #894, #713).
+- TextUnformatted(): Fixed a case where large-text path would read bytes past the text_end marker depending
+  on the position of new lines in the buffer (it wasn't affecting the output but still not the right thing to do!) 
 - BeginMenu(): Fixed menu popup horizontal offset being off the item in the menu bar when WindowPadding=0.0f.
 - ArrowButton(): Fixed arrow shape being horizontally misaligned by (FramePadding.y-FramePadding.x) if they are different.
 - Drag and Drop: Added GetDragDropPayload() to peek directly into the payload (if any) from anywhere. (#143)

imgui.cpp

@@ -1203,10 +1203,8 @@ char* ImStrdup(const char *str)
 
 const char* ImStrchrRange(const char* str, const char* str_end, char c)
 {
-    for ( ; str < str_end; str++)
-        if (*str == c)
-            return str;
-    return NULL;
+    const char* p = (const char*)memchr(str, (int)c, str_end - str);
+    return p;
 }
 
 int ImStrlenW(const ImWchar* str)
@@ -1216,6 +1214,13 @@ int ImStrlenW(const ImWchar* str)
     return n;
 }
 
+// Find end-of-line. Return pointer will point to either first \n, either str_end.
+const char* ImStreolRange(const char* str, const char* str_end)
+{
+    const char* p = (const char*)memchr(str, '\n', str_end - str);
+    return p ? p : str_end;
+}
+
 const ImWchar* ImStrbolW(const ImWchar* buf_mid_line, const ImWchar* buf_begin) // find beginning-of-line
 {
     while (buf_mid_line > buf_begin && buf_mid_line[-1] != '\n')
@@ -8343,29 +8348,17 @@ void ImGui::LogRenderedText(const ImVec2* ref_pos, const char* text, const char*
     for (;;)
     {
         // Split the string. Each new line (after a '\n') is followed by spacing corresponding to the current depth of our log entry.
-        const char* line_end = text_remaining;
-        while (line_end < text_end)
-            if (*line_end == '\n')
-                break;
-            else
-                line_end++;
-        if (line_end >= text_end)
-            line_end = NULL;
-
-        const bool is_first_line = (text == text_remaining);
-        bool is_last_line = false;
-        if (line_end == NULL)
+        const char* line_start = text_remaining;
+        const char* line_end = ImStreolRange(line_start, text_end);
+        const bool is_first_line = (line_start == text);
+        const bool is_last_line = (line_end == text_end);
+        if (!is_last_line || (line_start != line_end))
         {
-            is_last_line = true;
-            line_end = text_end;
-        }
-        if (line_end != NULL && !(is_last_line && (line_end - text_remaining)==0))
-        {
-            const int char_count = (int)(line_end - text_remaining);
+            const int char_count = (int)(line_end - line_start);
             if (log_new_line || !is_first_line)
-                LogText(IM_NEWLINE "%*s%.*s", tree_depth*4, "", char_count, text_remaining);
+                LogText(IM_NEWLINE "%*s%.*s", tree_depth*4, "", char_count, line_start);
             else
-                LogText(" %.*s", char_count, text_remaining);
+                LogText(" %.*s", char_count, line_start);
         }
 
         if (is_last_line)

imgui_internal.h

@@ -141,7 +141,8 @@ IMGUI_API void          ImStrncpy(char* dst, const char* src, size_t count);
 IMGUI_API char*         ImStrdup(const char* str);
 IMGUI_API const char*   ImStrchrRange(const char* str_begin, const char* str_end, char c);
 IMGUI_API int           ImStrlenW(const ImWchar* str);
-IMGUI_API const ImWchar*ImStrbolW(const ImWchar* buf_mid_line, const ImWchar* buf_begin); // Find beginning-of-line
+IMGUI_API const char*   ImStreolRange(const char* str, const char* str_end);                // End end-of-line
+IMGUI_API const ImWchar*ImStrbolW(const ImWchar* buf_mid_line, const ImWchar* buf_begin);   // Find beginning-of-line
 IMGUI_API const char*   ImStristr(const char* haystack, const char* haystack_end, const char* needle, const char* needle_end);
 IMGUI_API void          ImStrTrimBlanks(char* str);
 IMGUI_API int           ImFormatString(char* buf, size_t buf_size, const char* fmt, ...) IM_FMTARGS(3);

imgui_widgets.cpp

@@ -133,8 +133,9 @@ void ImGui::TextUnformatted(const char* text, const char* text_end)
     {
         // Long text!
         // Perform manual coarse clipping to optimize for long multi-line text
-        // From this point we will only compute the width of lines that are visible. Optimization only available when word-wrapping is disabled.
-        // We also don't vertically center the text within the line full height, which is unlikely to matter because we are likely the biggest and only item on the line.
+        // - From this point we will only compute the width of lines that are visible. Optimization only available when word-wrapping is disabled.
+        // - We also don't vertically center the text within the line full height, which is unlikely to matter because we are likely the biggest and only item on the line.
+        // - We use memchr(), pay attention that well optimized versions of those str/mem functions are much faster than a casually written loop.
         const char* line = text;
         const float line_height = GetTextLineHeight();
         const ImRect clip_rect = window->ClipRect;
@@ -153,7 +154,7 @@ void ImGui::TextUnformatted(const char* text, const char* text_end)
                     int lines_skipped = 0;
                     while (line < text_end && lines_skipped < lines_skippable)
                     {
-                        const char* line_end = strchr(line, '\n');
+                        const char* line_end = (const char*)memchr(line, '\n', text_end - line);
                         if (!line_end)
                             line_end = text_end;
                         line = line_end + 1;
@@ -169,15 +170,15 @@ void ImGui::TextUnformatted(const char* text, const char* text_end)
                 ImRect line_rect(pos, pos + ImVec2(FLT_MAX, line_height));
                 while (line < text_end)
                 {
-                    const char* line_end = strchr(line, '\n');
                     if (IsClippedEx(line_rect, 0, false))
                         break;
 
+                    const char* line_end = (const char*)memchr(line, '\n', text_end - line);
+                    if (!line_end)
+                        line_end = text_end;
                     const ImVec2 line_size = CalcTextSize(line, line_end, false);
                     text_size.x = ImMax(text_size.x, line_size.x);
                     RenderText(pos, line, line_end, false);
-                    if (!line_end)
-                        line_end = text_end;
                     line = line_end + 1;
                     line_rect.Min.y += line_height;
                     line_rect.Max.y += line_height;
@@ -188,7 +189,7 @@ void ImGui::TextUnformatted(const char* text, const char* text_end)
                 int lines_skipped = 0;
                 while (line < text_end)
                 {
-                    const char* line_end = strchr(line, '\n');
+                    const char* line_end = (const char*)memchr(line, '\n', text_end - line);
                     if (!line_end)
                         line_end = text_end;
                     line = line_end + 1;