Spin Input Widget - Int/Float/Double

[Al]

Dear ImGui 1.72 WIP (17101)

sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201703
define: APPLE
define: GNUC=4
define: clang_version=10.0.1 (clang-1001.0.46.4)

io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_opengl3

I was looking for a classic spinner input (int input with up/down arrows on right), but could not find anything. Of course this is basically the same as InputInt etc but replacing the +/- buttons with arrow buttons just improving the look.

I implemented based on InputScalar(), and modifying the +/- button code to use ArrowButtons within a group in order to stack the arrows. The only issue/hack is the ImGui ArrowButton/RenderArrow methods are dependent on the FontSize. So in order to properly scale the arrow buttons down I had to override/restore the current FontSize. Perhaps there is a better way.

The code below defines SpinInt/SpinScalar as I did not want to change the current widgets. The portion that is different from InputScalar is blocked with start/end diff comments.

Example:

Hopefully someone will find this useful.

namespace ImGui
{
	IMGUI_API bool SpinScaler(const char* label, ImGuiDataType data_type, void* data_ptr, const void* step, const void* step_fast, const char* format, ImGuiInputTextFlags flags);
	IMGUI_API bool SpinInt(const char* label, int* v, int step = 1, int step_fast = 100, ImGuiInputTextFlags flags = 0);
	IMGUI_API bool SpinFloat(const char* label, float* v, float step = 0.0f, float step_fast = 0.0f, const char* format = "%.3f", ImGuiInputTextFlags flags = 0);
	IMGUI_API bool SpinDouble(const char* label, double* v, double step = 0.0, double step_fast = 0.0, const char* format = "%.6f", ImGuiInputTextFlags flags = 0);
};

bool ImGui::SpinScaler(const char* label, ImGuiDataType data_type, void* data_ptr, const void* step, const void* step_fast, const char* format, ImGuiInputTextFlags flags)
{
	ImGuiWindow* window = GetCurrentWindow();
	if (window->SkipItems)
		return false;

	ImGuiContext& g = *GImGui;
	ImGuiStyle& style = g.Style;

	if (format == NULL)
		format = DataTypeGetInfo(data_type)->PrintFmt;

	char buf[64];
	DataTypeFormatString(buf, IM_ARRAYSIZE(buf), data_type, data_ptr, format);

	bool value_changed = false;
	if ((flags & (ImGuiInputTextFlags_CharsHexadecimal | ImGuiInputTextFlags_CharsScientific)) == 0)
		flags |= ImGuiInputTextFlags_CharsDecimal;
	flags |= ImGuiInputTextFlags_AutoSelectAll;
	flags |= ImGuiInputTextFlags_NoMarkEdited;  // We call MarkItemEdited() ourselve by comparing the actual data rather than the string.

	if (step != NULL)
	{
		const float button_size = GetFrameHeight();

		BeginGroup(); // The only purpose of the group here is to allow the caller to query item data e.g. IsItemActive()
		PushID(label);
		SetNextItemWidth(ImMax(1.0f, CalcItemWidth() - (button_size + style.ItemInnerSpacing.x) * 2));
		if (InputText("", buf, IM_ARRAYSIZE(buf), flags)) // PushId(label) + "" gives us the expected ID from outside point of view
			value_changed = DataTypeApplyOpFromText(buf, g.InputTextState.InitialTextA.Data, data_type, data_ptr, format);

		// Step buttons
		const ImVec2 backup_frame_padding = style.FramePadding;
		style.FramePadding.x = style.FramePadding.y;
		ImGuiButtonFlags button_flags = ImGuiButtonFlags_Repeat | ImGuiButtonFlags_DontClosePopups;
		if (flags & ImGuiInputTextFlags_ReadOnly)
			button_flags |= ImGuiButtonFlags_Disabled;
		SameLine(0, style.ItemInnerSpacing.x);

// start diffs
		float frame_height = GetFrameHeight();
		float arrow_size = std::floor(frame_height * .45f);
		float arrow_spacing = frame_height - 2.0f * arrow_size;

		BeginGroup();
		PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2{g.Style.ItemSpacing.x, arrow_spacing});

		// save/change font size to draw arrow buttons correctly
		float org_font_size = GetDrawListSharedData()->FontSize;
		GetDrawListSharedData()->FontSize = arrow_size;

		if (ArrowButtonEx("+", ImGuiDir_Up, ImVec2(arrow_size, arrow_size), button_flags))
		{
			DataTypeApplyOp(data_type, '+', data_ptr, data_ptr, g.IO.KeyCtrl && step_fast ? step_fast : step);
			value_changed = true;
		}

		if (ArrowButtonEx("-", ImGuiDir_Down, ImVec2(arrow_size, arrow_size), button_flags))
		{
			DataTypeApplyOp(data_type, '-', data_ptr, data_ptr, g.IO.KeyCtrl && step_fast ? step_fast : step);
			value_changed = true;
		}

		// restore font size
		GetDrawListSharedData()->FontSize = org_font_size;

		PopStyleVar(1);
		EndGroup();
// end diffs

		const char* label_end = FindRenderedTextEnd(label);
		if (label != label_end)
		{
			SameLine(0, style.ItemInnerSpacing.x);
			TextEx(label, label_end);
		}
		style.FramePadding = backup_frame_padding;

		PopID();
		EndGroup();
	}
	else
	{
		if (InputText(label, buf, IM_ARRAYSIZE(buf), flags))
			value_changed = DataTypeApplyOpFromText(buf, g.InputTextState.InitialTextA.Data, data_type, data_ptr, format);
	}
	if (value_changed)
		MarkItemEdited(window->DC.LastItemId);

	return value_changed;
}

bool ImGui::SpinInt(const char* label, int* v, int step, int step_fast, ImGuiInputTextFlags flags)
{
	// Hexadecimal input provided as a convenience but the flag name is awkward. Typically you'd use InputText() to parse your own data, if you want to handle prefixes.
	const char* format = (flags & ImGuiInputTextFlags_CharsHexadecimal) ? "%08X" : "%d";
	return SpinScaler(label, ImGuiDataType_S32, (void*)v, (void*)(step>0 ? &step : NULL), (void*)(step_fast>0 ? &step_fast : NULL), format, flags);
}

bool ImGui::SpinFloat(const char* label, float* v, float step, float step_fast, const char* format, ImGuiInputTextFlags flags)
{
	flags |= ImGuiInputTextFlags_CharsScientific;
	return SpinScaler(label, ImGuiDataType_Float, (void*)v, (void*)(step>0.0f ? &step : NULL), (void*)(step_fast>0.0f ? &step_fast : NULL), format, flags);
}

bool ImGui::SpinDouble(const char* label, double* v, double step, double step_fast, const char* format, ImGuiInputTextFlags flags)
{
	flags |= ImGuiInputTextFlags_CharsScientific;
	return SpinScaler(label, ImGuiDataType_Double, (void*)v, (void*)(step>0.0 ? &step : NULL), (void*)(step_fast>0.0 ? &step_fast : NULL), format, flags);
}