Method NavScoreItem

KBotExt/imgui/imgui.cpp:10845–10981

Scoring function for gamepad/keyboard directional navigation. Based on https://gist.github.com/rygorous/6981057

// Scoring function for gamepad/keyboard directional navigation. Based on https://gist.github.com/rygorous/6981057
static bool ImGui::NavScoreItem(ImGuiNavItemData* result)
{
	ImGuiContext& g = *GImGui;
	ImGuiWindow* window = g.CurrentWindow;
	if (g.NavLayer != window->DC.NavLayerCurrent)
		return false;

	// FIXME: Those are not good variables names
	ImRect cand = g.LastItemData.NavRect;   // Current item nav rectangle
	const ImRect curr = g.NavScoringRect;   // Current modified source rect (NB: we've applied Max.x = Min.x in NavUpdate() to inhibit the effect of having varied item width)
	g.NavScoringDebugCount++;

	// When entering through a NavFlattened border, we consider child window items as fully clipped for scoring
	if (window->ParentWindow == g.NavWindow)
	{
		IM_ASSERT((window->Flags | g.NavWindow->Flags) & ImGuiWindowFlags_NavFlattened);
		if (!window->ClipRect.Overlaps(cand))
			return false;
		cand.ClipWithFull(window->ClipRect); // This allows the scored item to not overlap other candidates in the parent window
	}

	// Compute distance between boxes
	// FIXME-NAV: Introducing biases for vertical navigation, needs to be removed.
	float dbx = NavScoreItemDistInterval(cand.Min.x, cand.Max.x, curr.Min.x, curr.Max.x);
	float dby = NavScoreItemDistInterval(ImLerp(cand.Min.y, cand.Max.y, 0.2f), ImLerp(cand.Min.y, cand.Max.y, 0.8f), ImLerp(curr.Min.y, curr.Max.y, 0.2f), ImLerp(curr.Min.y, curr.Max.y, 0.8f)); // Scale down on Y to keep using box-distance for vertically touching items
	if (dby != 0.0f && dbx != 0.0f)
		dbx = (dbx / 1000.0f) + ((dbx > 0.0f) ? +1.0f : -1.0f);
	float dist_box = ImFabs(dbx) + ImFabs(dby);

	// Compute distance between centers (this is off by a factor of 2, but we only compare center distances with each other so it doesn't matter)
	float dcx = (cand.Min.x + cand.Max.x) - (curr.Min.x + curr.Max.x);
	float dcy = (cand.Min.y + cand.Max.y) - (curr.Min.y + curr.Max.y);
	float dist_center = ImFabs(dcx) + ImFabs(dcy); // L1 metric (need this for our connectedness guarantee)

	// Determine which quadrant of 'curr' our candidate item 'cand' lies in based on distance
	ImGuiDir quadrant;
	float dax = 0.0f, day = 0.0f, dist_axial = 0.0f;
	if (dbx != 0.0f || dby != 0.0f)
	{
		// For non-overlapping boxes, use distance between boxes
		dax = dbx;
		day = dby;
		dist_axial = dist_box;
		quadrant = ImGetDirQuadrantFromDelta(dbx, dby);
	}
	else if (dcx != 0.0f || dcy != 0.0f)
	{
		// For overlapping boxes with different centers, use distance between centers
		dax = dcx;
		day = dcy;
		dist_axial = dist_center;
		quadrant = ImGetDirQuadrantFromDelta(dcx, dcy);
	}
	else
	{
		// Degenerate case: two overlapping buttons with same center, break ties arbitrarily (note that LastItemId here is really the _previous_ item order, but it doesn't matter)
		quadrant = (g.LastItemData.ID < g.NavId) ? ImGuiDir_Left : ImGuiDir_Right;
	}