[Feature] Pie chart: no text and specify colors

[CosminPerRam]

Feature description
Hey! Some time ago I made a sorting visualizer by utilizing this great library and I'd like to add support for visualizing via pie plots, but I can't exactly do this as I'd like because:

1. I can't specify what color I'd like an element to have (see photo 1)
2. I can't hide the element's text (see photo 2)

Additionally, if it's possible I'd like to be able to set the weight/size of each element to be an equal amount to each (this is very visible in photo 1, the 12'o'clock right element is bigger than the left one).

Feature videos/screenshots
Below I have attached some context screenshots amongst with some very ugly and hacky changes I attempted to made.

Photo 1: Can't specify colors for the pie elements.

Fix: Called a custom function here to generate a color based on the element's value.

implot/implot_items.cpp

Line 2302 in 81b8b19

ImU32 col = GetCurrentItem()->Color;

Photo 2: Can't hide element's text

Fix: removed these lines

implot/implot_items.cpp

Lines 2363 to 2364 in 81b8b19

	ImU32 col = CalcTextColor(ImGui::ColorConvertU32ToFloat4(item->Color));
	draw_list.AddText(pos - size * 0.5f, col, buffer);

Photo 3: With both limits mitigated, this is something I'd like to have (note that the additional request I mentioned isn't that visible now).

The first problem (and the additional one) could maybe be solved via a flag, but for the second I'm not sure what the best solution would be.
These requests sound a bit odd for a normal pie chart usecase but if these are not fit to be made for this library that's fine.
If this issue could have better been split into separate ones please mention to do so and close this one.
I'm sorry if I missed the obvious, haven't touched implot/imgui for a long while, thanks for the wonderful library and welcome new maintainer (:

[brenocq]

Hi @CosminPerRam!

I can't specify what color I'd like an element to have (see photo 1)

As far as I know, there's no nice way of doing this. Per-slice colors can be introduced together with #519.

I can't hide the element's text (see photo 2)

To not show the element labels, you can set the label_fmt to "". Looks like it crashes if you try to set it to nullptr... 🐛

// Plots a pie chart. Center and radius are in plot units. #label_fmt can be set to nullptr for no labels.
IMPLOT_TMP void PlotPieChart(const char* const label_ids[], const T* values, int count, double x, double y, double radius, ImPlotFormatter fmt, void* fmt_data=nullptr, double angle0=90, ImPlotPieChartFlags flags=0);
IMPLOT_TMP void PlotPieChart(const char* const label_ids[], const T* values, int count, double x, double y, double radius, const char* label_fmt="%.1f", double angle0=90, ImPlotPieChartFlags flags=0);

Additionally, if it's possible I'd like to be able to set the weight/size of each element to be an equal amount to each (this is very visible in photo 1, the 12'o'clock right element is bigger than the left one).

Currently, if you want all slices to have the same size, they would need to have the same value. Maybe it would be a nice idea for you to do custom rendering (render triangles to ImPlot's plot using the ImGui draw list directly), this way you would have the full freedom to specify the color and size of each slice.