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2000-11-13 Mathieu Lacage <mathieu@eazel.com> Buddy: pavel. Fix bug 2422 and 4382. * components/tree/nautilus-tree-view.c: (filtering_changed_callback), (collapse_time_callback): added. collapses opened folders when you leave the tree view. (nautilus_tree_view_drag_leave): make it call tree_view_drag_destroy (nautilus_tree_view_drag_motion): cleanup, make it call tree_view_drag_destroy_real (nautilus_tree_view_drag_drop): spaces. (nautilus_tree_view_drag_data_received): cleanup: make it call tree_view_drag_destroy. (nautilus_dump_info): cleanup. (expand_time_callback): cleanup. (nautilus_tree_view_expand_maybe_later): cleanup (nautilus_tree_view_collapse_all): cleanup. (nautilus_tree_view_receive_dropped_icons): make it collapse correctly. (nautilus_tree_view_prelight_stop): new function: clears prelighting. (nautilus_tree_view_drag_destroy): new function: destroys when drag finished. (nautilus_tree_view_drag_destroy_real): new function: destroys when drag begins. * docs/dnd.txt: add some thoughts. * libnautilus-extensions/nautilus-drag.c: (nautilus_drag_init): init new field. * libnautilus-extensions/nautilus-drag.h: add shared field to public structure.
92 lines
3.1 KiB
Text
92 lines
3.1 KiB
Text
Nautilus dnd code.
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Nautilus dnd code is pretty compilcated, it has a lot of entry points and exit points.
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Trying to clarify this now.
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You have to implement:
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If you are a source:
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drag_begin
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drag_end
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drag_get_data
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If you are a destination:
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drag_motion
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drag_data_received
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drag_drop
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drag_leave
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1) Source
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---------
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if you are a source, you have to start a drag trough gtk_drag_begin.
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This will call drag_begin signal in the source.
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Then, when the destination calls gtk_drag_finish, drag_end will be
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called in the source.
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drag_get_data will be called in the source when the destination
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calls gtk_drag_get_data
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So, the source is very easy to write: it just needs to implement
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those 3 signals and it should not have any memory management issue.
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2) Destination
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--------------
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Things get a little bit complicated.
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when the dragging cursor gets in your window, you will get drag_motion
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events. In nautilus, we do many things in this function:
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- we start auto-scrolling if it is necessary.
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- we call nautilus_*_ensure_data
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- we prelight what is under the cursor if it can accept the drag.
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- we try to expand what is under you if it can accept the drop (tree view)
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nautilus_*_ensure_data is vital. It calls gtk_drag_get_data to get the
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data from the source. this allows the destination to store it in advance and use it
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to know if what is under the cursor can accept the drag.
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Then, when the drop occurs, drag_drop is called on the destination.
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drag_drop calls gtk_drag_get_data to get the data from the source to do its drop.
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Then, drag_data_received is called when the data is received.
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There, we can do the actual operation involved by the drop.
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Also, just before the drag_drop event, a drag_leave event is triggered.
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If no drop occurs, a drag_leave occurs.
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So, drag_data_received does 2 things: it is called to get the data when we are
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in motion and store it. It is also called to do the actual drop operation when
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a drop happened.
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So, drag_data_received usually does 2 tests: it tests if the data was received.
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If it was received, it stores it.
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Then it tests if the drop occured just before. If so, it does the operation.
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This schema involves careful memory management:
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1) 2 exit points in destination. (drag_leave and drag_data_received)
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2) a lot of things are done in the callbacks so you have to take into
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account all the possible code paths.
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To solve 1), we should use ONE destroy function which cleans up the drag data.
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To solve 2), we have to be very careful where we call this fution from.
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This function has to clean up:
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- the list of expanded nodes (tree view).
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- the autoscroll code.
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- the prelighting code.
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It also has to set drag_info->need_to_destroy to TRUE
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so that during the next drag in this widget, the
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rest of the drag data is destroyed before begening the actual
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new drag.
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When we receive a drag_motion, we first test for need_to_destroy and
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destroy the rest of the data left from the previous drag. This code
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has to destroy/reset:
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- the drag data.
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- the boolean vars used to store the state of the drag.
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