Fix: don't respond to mouse drag events that started outside of our nodes window - #238

…238)

A right-drag that started in another window panned the editor as soon as
the mouse entered it, since a pan only needed the button dragging and the
editor focused and hovered. A pan now also needs the press to have made
the editor's background or one of its objects the active item.

Co-authored-by: Jules Fouchy <jules.fouchy@ntymail.com>

…tton

Since the fix of thedmd#238, a pan needs the press to make the background or an object active.
A press on a widget of a node (a button, which uses the left mouse button) made neither: the view did not pan.

The background now takes a press of the navigate button inside the editor that no item owns (SetKeyOwner(), until release):
- a drag from such a widget pans;
- a widget that uses the navigate button owns it, and keeps it;
- a drag pressed outside the editor still does not pan (thedmd#238).

Needs Dear ImGui 1.90.7 (ImGuiKeyOwner_NoOwner). With an older one, nothing changes.

- from the background, and from a button of a node: the view pans;
- from a widget that uses the navigate button: it keeps the button, the view does not pan;
- from outside the editor: no pan when the drag enters it (thedmd#238).

…tton

Since the fix of thedmd#238, a pan needs the press to make the background or an object active.
A press on a widget of a node (a button, which uses the left mouse button) made neither: the view did not pan.

Now a press of the navigate button inside the editor that no item owns is remembered:
- once the mouse drags, the background takes the button until its release (SetKeyOwner()), and the view pans;
- a click stays a click: the context menus of the widget and of its node open, as before;
- a widget that uses the navigate button owns it, and keeps it;
- the release that ends a pan is locked for its frame: no context menu opens under the mouse;
- a drag pressed outside the editor still does not pan (thedmd#238).

Needs Dear ImGui 1.90.7 (ImGuiKeyOwner_NoOwner). With an older one, nothing changes.

- from the background, and from a button of a node: the view pans;
- from a widget that uses the navigate button: it keeps the button, no pan;
- from outside the editor: no pan (thedmd#238);
- a right click on a button of a node: its context menu and the node's, as before;
- a pan that ends on the button it started from: no context menu.

…tton

Since the fix of thedmd#238, a pan needs the press to make the background or an object active.
A press on a widget of a node (a button, which uses the left mouse button) made neither: the view did not pan.

Now a press of the navigate button inside the editor that no item owns is remembered:
- once the mouse drags, the background takes the button until its release (SetKeyOwner()), and the view pans;
- a click stays a click: the context menus of the widget and of its node open, as before;
- a widget that uses the navigate button owns it, and keeps it;
- the release that ends a pan is locked for its frame: no context menu opens under the mouse;
- a drag pressed outside the editor still does not pan (thedmd#238).

Needs Dear ImGui 1.90.7 (ImGuiKeyOwner_NoOwner). With an older one, nothing changes.

- from the background, and from a button of a node: the view pans;
- from a widget that uses the navigate button: it keeps the button, no pan;
- from outside the editor: no pan (thedmd#238);
- a right click on a button of a node: its context menu and the node's, as before;
- a pan that ends on the button it started from: no context menu.

…tton

Since the fix of thedmd#238, a pan needs the press to make the background or an object active.
A press on a widget of a node (a button, which uses the left mouse button) made neither: the view did not pan.

Now a press of the navigate button inside the editor that no item owns is remembered:
- once the mouse drags, the background takes the button until its release (SetKeyOwner()), and the view pans;
- a click stays a click: the context menus of the widget and of its node open, as before;
- a widget that uses the navigate button owns it, and keeps it;
- the release that ends a pan is locked for its frame: no context menu opens under the mouse;
- a drag pressed outside the editor still does not pan (thedmd#238).

Needs Dear ImGui 1.89 (input ownership). With an older one, nothing changes.

- from the background, and from a button of a node: the view pans;
- from a widget that uses the navigate button: it keeps the button, no pan;
- from outside the editor: no pan (thedmd#238);
- a right click on a button of a node: its context menu and the node's, as before;
- a pan that ends on the button it started from: no context menu.

The pan from a button, and the end of a pan, need the fix: skipped before Dear ImGui 1.89.

…tton

Since the fix of thedmd#238, a pan needs the press to make the background or an object active.
A press on a widget of a node (a button, which uses the left mouse button) made neither: the view did not pan.

Now a press of the navigate button inside the editor that no item owns is remembered:
- once the mouse drags, the background takes the button until its release (SetKeyOwner()), and the view pans;
- a click stays a click: the context menus of the widget and of its node open, as before;
- a widget that uses the navigate button owns it, and keeps it;
- the release that ends a pan is locked for its frame: no context menu opens under the mouse;
- a drag pressed outside the editor still does not pan (thedmd#238).

Needs Dear ImGui 1.89 (input ownership). With an older one, nothing changes.

- from the background, and from a button of a node: the view pans;
- from a widget that uses the navigate button: it keeps the button, no pan;
- from outside the editor: no pan (thedmd#238);
- a right click on a button of a node: its context menu and the node's, as before;
- a pan that ends on the button it started from: no context menu.

The pan from a button, and the end of a pan, need the fix: skipped before Dear ImGui 1.89.