90 lines
3.8 KiB
Plaintext
90 lines
3.8 KiB
Plaintext
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contexts.txt
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============
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Introduction
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------------
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This file describes how PikaContexts are used in PIKA.
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Overview
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--------
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One important context is the so called "user context",
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pika_get_user_context(). This context keeps track on what image the
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user currently has active, for example. Dock windows have their own
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context which does not necessarily mirror the user context. A dock
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window can be set to show information for a specific image. Plug-ins
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also have their own context.
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Communication between contexts
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------------------------------
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So how do the various contexts synchronize and propagate changes?
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This is most easily explained by a sequence diagram. Let's say there
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are two image windows with different images opened in PIKA. Call them
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A and B. Let's say A is currently active. When the user activates B,
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this is the sequence of events from the focus event to the layers
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dockable have been updated with the new image. To understand the
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diagram, you have to know that the dock window has connected signal
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handlers to image changes in the user context (through a dialog
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factory getter), and the layer dockable have connected a signal
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handler to image changes in the dock window context. The sequence of
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events is as follows:
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PikaContext PikaContext PikaItemTreeView,
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PikaDisplayShell user PikaDockWindow dock window PikaLayerTreeView
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focus event | | | |
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------->| | | | |
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| pika_context_set_display() | | |
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|--------------->|----------+ | | |
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| pika_context_set_image() | | | |
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| |<---------+ | | |
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| | "image-changed" | |
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| |------------->| | |
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| | | pika_context_set_image() |
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| | |------------->| |
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| | | | "image-changed" /
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| | | | set_image()
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| | | |------------>|
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In single-window mode, the dockables listen directly to the user
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context. When switching between single-window and multi-window modes,
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the dockables are updated with their new context, just as when moving
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a dockable between different dock windows and thus also different
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contexts. The sequence diagram for single-window mode is:
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PikaContext PikaItemTreeView
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PikaDisplayShell user PikaLayerTreeView
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focus event | |
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------->| | |
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| pika_context_set_display() |
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|--------------->|----------+ |
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| pika_context_set_image() | |
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| |<---------+ |
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| | "image-changed" /
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| | set_image()
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| |------------->|
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Parent/child relationships
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--------------------------
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TODO
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