ImFormatString, ImFormatStringV(): clarifying specs so that passing a NULL buffer should return the desired length. (#1038)
diff --git a/imgui.cpp b/imgui.cpp
index fd1c44d..6d2ff61 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -1010,16 +1010,18 @@
return src;
}
-// MSVC version appears to return -1 on overflow, whereas glibc appears to return total count (which may be >= buf_size).
+// A) MSVC version appears to return -1 on overflow, whereas glibc appears to return total count (which may be >= buf_size).
// Ideally we would test for only one of those limits at runtime depending on the behavior the vsnprintf(), but trying to deduct it at compile time sounds like a pandora can of worm.
+// B) When buf==NULL vsnprintf() will return the output size.
#ifndef IMGUI_DISABLE_FORMAT_STRING_FUNCTIONS
int ImFormatString(char* buf, int buf_size, const char* fmt, ...)
{
- IM_ASSERT(buf_size > 0);
va_list args;
va_start(args, fmt);
int w = vsnprintf(buf, buf_size, fmt, args);
va_end(args);
+ if (buf == NULL)
+ return w;
if (w == -1 || w >= buf_size)
w = buf_size - 1;
buf[w] = 0;
@@ -1028,8 +1030,9 @@
int ImFormatStringV(char* buf, int buf_size, const char* fmt, va_list args)
{
- IM_ASSERT(buf_size > 0);
int w = vsnprintf(buf, buf_size, fmt, args);
+ if (buf == NULL)
+ return w;
if (w == -1 || w >= buf_size)
w = buf_size - 1;
buf[w] = 0;
@@ -1671,7 +1674,7 @@
va_list args_copy;
va_copy(args_copy, args);
- int len = vsnprintf(NULL, 0, fmt, args); // FIXME-OPT: could do a first pass write attempt, likely successful on first pass.
+ int len = ImFormatStringV(NULL, 0, fmt, args); // FIXME-OPT: could do a first pass write attempt, likely successful on first pass.
if (len <= 0)
return;
@@ -1684,7 +1687,7 @@
}
Buf.resize(needed_sz);
- ImFormatStringV(&Buf[write_off] - 1, len+1, fmt, args_copy);
+ ImFormatStringV(&Buf[write_off - 1], len + 1, fmt, args_copy);
}
void ImGuiTextBuffer::append(const char* fmt, ...)
diff --git a/imgui_demo.cpp b/imgui_demo.cpp
index 35ee618..5fe78db 100644
--- a/imgui_demo.cpp
+++ b/imgui_demo.cpp
@@ -2359,6 +2359,7 @@
void AddLog(const char* fmt, ...) IM_FMTARGS(2)
{
+ // FIXME-OPT
char buf[1024];
va_list args;
va_start(args, fmt);
