ImSequencer: Don't expand to fill all space in the window

[idbrii]

Instead of expanding to fill available space, calculate the space we need and use that much.

If you have code roughly like:

    Sequencer(&mySequence, &currentFrame, &expanded, &selectedEntry, &firstFrame);
    float color[4];
    ImGui::ColorEdit4("Color", color);

you get blank space below imsequencer and can't see the widgets below it:

With this change, you can see the widgets below it.

However, the downside is that the thumb can scroll off the bottom of the window:

[CedricGuillemet]

Not sure about this one. You can set Imsequencer height from the available content height (minus your other controls).

[idbrii]

Is there a case where expand to fill is preferable?

You can set Imsequencer height from the available content height (minus your other controls).

Do you mean wrap Sequencer in Begin/EndChild? Doesn't that mean I need to determine the height of my widgets below ImSequencer so it can expand appropriately? Awkward when using a bunch of CollapsingHeader:

static bool was_expanded = false;
ImVec2 sequencer_size = ImGui::GetContentRegionAvail();
sequencer_size.y -= 20;
if (was_expanded) {
    sequencer_size.y -= 25 * 2;
}

ImGui::BeginChild("Sequencer", sequencer_size);
{
    Sequencer(&mySequence, &currentFrame, &expanded, &selectedEntry, &firstFrame, ImSequencer::SEQUENCER_EDIT_ALL);
}
ImGui::EndChild();

was_expanded = ImGui::CollapsingHeader("Colors");
if (was_expanded) {
    float color[4];
    ImGui::ColorEdit4("Color", color);
    ImGui::ColorEdit4("Another Color", color);
}

And if I have lots of controls underneath, then imgui adds scrolling and ImSequencer doesn't clip properly while scrolling (probably fixable in master by just taking 6f60505):

With this PR, you don't get that clip badness. You will get double scrollbars, but I'm not sure why.

---

Regardless, assuming the normal use of ImSequencer is selecting an item and then using additional ImGui widgets below the sequencer to display data for that item, I'd think you want that flow it be easiest -- automatically figure out our height so widgets below will display.

[idbrii]

Rebased on master now that some of the old commits in here are merged and the issues from my previous comment are fixed.

"the downside is that the thumb can scroll off the bottom of the window" is still an issue and that's probably the main blocker to getting this merged. Doubtful I'll have time to address that soon.