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Add constexpr alternatives to public macros

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Macros can't be exported from a C++20 module, and they ignore scope
and type in any case. Add typed constexpr equivalents for the values
people commonly use: version, payload types, unicode limits, colour
packing, IM_COUNTOF() and IMGUI_CHECKVERSION(). Each is defined from
its macro, so the two always agree, including when imconfig.h
overrides them.

They need C++17 inline variables, so they sit behind
IMGUI_HAS_CONSTEXPR and C++11 builds are unaffected.
This commit is contained in:
Sharadh Rajaraman 2026-09-28 16:18:32 +01:00
parent 59a85207cc
commit f3dd5566c6
2 changed files with 46 additions and 0 deletions
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40
imgui.h
View File

@ -47,6 +47,7 @@ Index of this file:
// [SECTION] Font API (ImFontConfig, ImFontGlyph, ImFontGlyphRangesBuilder, ImFontAtlasFlags, ImFontAtlas, ImFontBaked, ImFont)
// [SECTION] Viewports (ImGuiViewportFlags, ImGuiViewport)
// [SECTION] ImGuiPlatformIO + other Platform Dependent Interfaces (ImGuiPlatformImeData)
// [SECTION] Constexpr alternatives to macros
// [SECTION] Obsolete functions and types
*/
@ -4010,6 +4011,45 @@ struct ImGuiPlatformImeData
ImGuiPlatformImeData() { memset((void*)this, 0, sizeof(*this)); }
};
//-----------------------------------------------------------------------------
// [SECTION] Constexpr alternatives to macros
// (requires C++17: see IMGUI_HAS_CONSTEXPR in imgui_macros.h)
//-----------------------------------------------------------------------------
#ifdef IMGUI_HAS_CONSTEXPR
// Version (= IMGUI_VERSION, IMGUI_VERSION_NUM)
inline constexpr char ImGuiVersion[] = IMGUI_VERSION;
inline constexpr int ImGuiVersionNum = IMGUI_VERSION_NUM;
// Standard Drag and Drop payload types (= IMGUI_PAYLOAD_TYPE_COLOR_3F, IMGUI_PAYLOAD_TYPE_COLOR_4F)
inline constexpr char ImGuiPayloadType_Color3F[] = IMGUI_PAYLOAD_TYPE_COLOR_3F;
inline constexpr char ImGuiPayloadType_Color4F[] = IMGUI_PAYLOAD_TYPE_COLOR_4F;
// Unicode (= IM_UNICODE_CODEPOINT_INVALID, IM_UNICODE_CODEPOINT_MAX)
inline constexpr ImWchar32 ImUnicodeCodepoint_Invalid = IM_UNICODE_CODEPOINT_INVALID;
inline constexpr ImWchar32 ImUnicodeCodepoint_Max = IM_UNICODE_CODEPOINT_MAX;
// 32-bit encoded colors (= IM_COL32(), IM_COL32_WHITE, IM_COL32_BLACK, IM_COL32_BLACK_TRANS, IM_COL32_X_SHIFT, IM_COL32_A_MASK)
constexpr ImU32 ImCol32(ImU32 r, ImU32 g, ImU32 b, ImU32 a) { return IM_COL32(r, g, b, a); }
inline constexpr ImU32 ImCol32_White = IM_COL32_WHITE;
inline constexpr ImU32 ImCol32_Black = IM_COL32_BLACK;
inline constexpr ImU32 ImCol32_BlackTrans = IM_COL32_BLACK_TRANS;
inline constexpr int ImCol32_RShift = IM_COL32_R_SHIFT;
inline constexpr int ImCol32_GShift = IM_COL32_G_SHIFT;
inline constexpr int ImCol32_BShift = IM_COL32_B_SHIFT;
inline constexpr int ImCol32_AShift = IM_COL32_A_SHIFT;
inline constexpr ImU32 ImCol32_AMask = IM_COL32_A_MASK;
// Size of a static C-style array (= IM_COUNTOF(), but won't compile with pointers)
template<typename T, size_t N> constexpr int ImCountOf(const T (&arr)[N]) { return IM_COUNTOF(arr); }
// Check that version and structures layouts are matching between compiled imgui code and caller (= IMGUI_CHECKVERSION())
namespace ImGui
{
inline bool CheckVersion() { return IMGUI_CHECKVERSION(); }
}
#endif // #ifdef IMGUI_HAS_CONSTEXPR
//-----------------------------------------------------------------------------
// [SECTION] Obsolete functions and types
// (Will be removed! Read 'API BREAKING CHANGES' section in imgui.cpp for details)

6
imgui_macros.h
View File

@ -36,6 +36,12 @@
#define IMGUI_IMPL_API IMGUI_API
#endif
// Constexpr alternatives to some of the macros below (e.g. ImCol32() for IM_COL32()) are declared in imgui.h ('Constexpr alternatives to macros' section) when compiling as C++17 or later.
// (C++17 is required for 'inline' variables)
#if (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L) || __cplusplus >= 201703L
#define IMGUI_HAS_CONSTEXPR
#endif
// Helper Macros
// (note: compiling with NDEBUG will usually strip out assert() to nothing, which is NOT recommended because we use asserts to notify of programmer mistakes.)
#ifndef IM_ASSERT