104 lines
3.5 KiB
Plaintext
104 lines
3.5 KiB
Plaintext
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The way that the GtkTreeView calculates sizing is pretty confusing.
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This is written down to help keep track of it in my head, and thus help
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anyone who hopes to work with the code in the future.
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-jrb
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HOW THE GTKTREEVIEW CALCULATES SIZE:
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====================================
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When the view is given a new model, the first thing it does is walk
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through the model at the top level, creating a GtkRBNode for each
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element of the model. Each node has a height of 0. The RBTree is kept
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updated as the models structure changes. Additionally, the user can
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expand, collapse, and select rows at this stage. The RBTree is accurate
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-- it just has a height of zero for every row.
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When the widget is realized, it calls install_presize_handler, to setup
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the first-run function. This is run before the expose event.
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HOW THE GTKTREEVIEWCOLUMN STORES SIZE:
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======================================
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There are a number of size related fields in the GtkTreeViewColumn
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structure. These are all valid after realization:
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column_type The sizing method to use when calculating the size
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of the column. Can be GROW_ONLY, AUTO, and FIXED.
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button_request The width as requested by the button.
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requested_width The width of the column as requested by the column.
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It is the max requested width of the bcells in the
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column. If the column_type is AUTO, then it is
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recalculated when a column changes. Otherwise, it
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only grows.
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resized_width The width after the user has resized the column.
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width The actual width of the column as displayed.
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fixed_width The requested fixed width for the column iff it's
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sizing type is set to GTK_TREE_VIEW_COLUMN_FIXED.
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Used instead of requested_width in that case.
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min_width The minimum width the column can be. If set to -1,
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this field is considered unset.
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max_width The maximum width the column can be. This can be
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overridden for the last column, if the tree_view is
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actually wider than the sum of all of the columns
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requested_widths. If set to -1, this field is
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considered unset.
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use_resized_width Use resized_width to determine the size.
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--
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tree_view->priv->width = the width the widget wants to be, including headers.
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tree_view->priv->height = the height the widget requests. It's the sum
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of the width of all visible columns.
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Both of these are calculated in _gtk_tree_view_update_size
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--
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The following invariants are true:
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min_width is less than or equal to width
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max_width is greater than or equal to width
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min_width <= max_width
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(sizing == GTK_TREE_VIEW_COLUMN_FIXED) => (requested_width == fixed_width)
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(column != last visible column) => width == CLAMP (requested_width, min_width, max_width)
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HOW THE VERTICAL OFFSET IS CALCULATED
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(This has nothing to do with columns)
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=====================================
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The current offset of the tree is determined by:
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tree_view->priv->dy
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All motion/button/expose events take this as the offset when trying to
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draw the tree. There are also two other related members:
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tree_view->priv->top_row
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tree_view->priv->top_row_dy
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In general _gtk_rbtree_node_find_offset (tree_view->priv->top_row) +
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tree_view->priv->top_row_dy is the same as tree_view->priv->dy.
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We have the alternate method so we can update dy when the tree changes.
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There are two functions:
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gtk_tree_view_dy_to_top_row
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and
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gtk_tree_view_top_row_to_dy
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They are called when the tree's confirmation changes, in order to sync
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the value appropriately. Note that these two functions sometimes call
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each other to negotiate a correct value if needed.
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