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MultiSelect: Demo: Remove UserDataToIndex from ExampleSelectionAdapter.

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Seems to make a better demo this way.
This commit is contained in:
ocornut 2023-09-01 16:09:41 +02:00
parent 8c1f659b3d
commit 530155d85a
1 changed files with 16 additions and 19 deletions
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31
imgui_demo.cpp
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@ -2761,26 +2761,27 @@ static void ShowDemoWindowWidgets()
}
}
// We use a little extra indirection layer here in order to use and demonstrate different ways to
// - identify items in the multi-selection system (using index? using identifiers? using pointers?)
// - store our persistent selection data (using index? using identifiers? using pointers?)
// Our multi-selection system doesn't make assumption about:
// - how you want to identify items in multi-selection API? Indices(*) / Custom Identifiers / Pointers ?
// - how you want to store persistent selection data? Indices / Custom Identifiers(*) / Pointers ?
// (*) This is the suggested solution: pass indices to API (because easy to iterate/interpolate) + persist your custom identifiers inside selection data.
// In this demo we:
// - always use indices in the multi-selection API (passed to SetNextItemSelectionUserData(), retrieved in ImGuiMultiSelectIO)
// - use a little extra indirection layer in order to abstract how persistent selection data is derived from an index.
// - in some cases we use Index as custom identifier, in some cases we read from some custom item data structure.
// Many combinations are possible depending on how you prefer to store your items and how you prefer to store your selection.
// WHEN YOUR APPLICATION SETTLES ON A CHOICE, YOU WILL PROBABLY PREFER TO GET RID OF THIS UNNECESSARY 'ExampleSelectionAdapter' INDIRECTION LOGIC.
// In theory we could add a IndexToUserData() function which would be used when calling SetNextItemSelectionUserData(), but omitting it makes things clearer.
// In theory, for maximum abstraction, this class could contains IndexToUserData() and UserDataToIndex() functions,
// but because we always use indices in SetNextItemSelectionUserData() in the demo, we omit that for clarify.
struct ExampleSelectionAdapter
{
void* Data = NULL;
int (*UserDataToIndex)(ExampleSelectionAdapter* self, ImGuiSelectionUserData item_data); // Function to convert item ImGuiSelectionUserData to item index
ImGuiID (*IndexToStorage)(ExampleSelectionAdapter* self, int idx); // Function to convert item index to data stored in persistent selection
ExampleSelectionAdapter() { SetupForDirectIndexes(); }
// Example for the simplest case: UserData==Index==SelectionStorage (this adapter doesn't even need to use the item data field)
void SetupForDirectIndexes()
{
UserDataToIndex = [](ExampleSelectionAdapter*, ImGuiSelectionUserData item_data) { return (int)item_data; }; // No transform: Pass indices to SetNextItemSelectionUserData()
IndexToStorage = [](ExampleSelectionAdapter*, int idx) { return (ImGuiID)idx; }; // No transform: Store indices inside persistent selection storage
}
// Example for the simplest case: Index==SelectionStorage (this adapter doesn't even need to use the item data field)
void SetupForDirectIndexes() { IndexToStorage = [](ExampleSelectionAdapter*, int idx) { return (ImGuiID)idx; }; }
};
// [Advanced] Helper class to store multi-selection state, used by the BeginMultiSelect() demos.
@ -2830,7 +2831,7 @@ struct ExampleSelection
// if (ms_io->RequestSetRange) { for (int n = (int)ms_io->RangeFirstItem; n <= (int)ms_io->RangeLastItem; n++) { UpdateItem(n, ms_io->RangeSelected); } }
void ApplyRequests(ImGuiMultiSelectIO* ms_io, ExampleSelectionAdapter* adapter, int items_count)
{
IM_ASSERT(adapter->UserDataToIndex != NULL && adapter->IndexToStorage != NULL);
IM_ASSERT(adapter->IndexToStorage != NULL);
if (ms_io->RequestClear || ms_io->RequestSelectAll)
Clear();
@ -2840,13 +2841,9 @@ struct ExampleSelection
AddItem(adapter->IndexToStorage(adapter, idx));
if (ms_io->RequestSetRange)
{
int first_item_idx = adapter->UserDataToIndex(adapter, ms_io->RangeFirstItem);
int last_item_idx = adapter->UserDataToIndex(adapter, ms_io->RangeLastItem);
for (int idx = first_item_idx; idx <= last_item_idx; idx++)
for (int idx = (int)ms_io->RangeFirstItem; idx <= (int)ms_io->RangeLastItem; idx++)
UpdateItem(adapter->IndexToStorage(adapter, idx), ms_io->RangeSelected);
}
}
// Call after BeginMultiSelect().
// - Calculate and set ms_io->RequestFocusItem, which we will focus during the loop.