Windows with (0,0) size should fit content about imgui

[ocornut]

I made it that (0,0) perform auto-sizing even on a window with NoResize flag.
Also added a SetWindowSize() entry point.
Let me know if it's alright for you.

[ocornut]

Could you clarify what you are reporting with code sample and a screenshot?

At the time of first creating a window with (0,0) size the window should automatically readjust to content size by gathering the maximum content frame over the next frame or two.
Double-clicking on a lower-right corner also fit the window.

However note that if your code is using window size to size widgets then auto-fitting create a feedback loop, so every auto-fitting will slightly readjust the window size.

[ebriney]

Perhaps this is because my window has the ImGuiWindowFlags_NoResize flags indeed.

[ocornut]

Correct! It currently skips all resizing behaviors with ImGuiWindowFlags_NoResize. Perhaps I should add a separate flag to distinguish manual user resize from initial auto-fit resize. Would you like that?

[ebriney]

A flag is ok, but you should assert if size <= 0 or set this flag.

[ocornut]

FYI I reorganised the Begin() functions which was full of traps (subtle ordering dependencies). It should be better and healthier now but there is the possibility that I've created bugs or changes of behavior related to window size. Let me know if you notice anything unusual.

The changes are spread over many commits ending with this
d84b573
(spreading them should make it easier to bissect for bugs shall we need to)