This project demonstrates a way to customize the class QListView of the Qt framework. It does not claim to be completed or
to provide and support a program for productive use. The usable versions are Qt5 (tested 5.15) and Qt6 (tested 6.4).
The main goals are:
- customize items,
- showing or hiding of section labels and
- sorting of these parts separately from each other.
The following diagram shows the developed classes starting with the abbreviation IB (Image Browser) and its relations to realize the goals. All classes with a starting Q are part of Qt framework.
This section descripts the realization of the named goals. All mentioned components are joined in class IBImageListWidget, which is implemented in the files ibimagelistwidget.hpp and ibimagelistwidget.cpp.
The customization of QListView items is very simple. Its generalizing class QAbstractItemView provides the possiblity to use an object of the class QAbstractItemDelegate which provides the method paint. The specializion to this class with the overriding of this method makes it possible to customize the items. The delegate class has another advantage. It supplies the size of an item for the QListView class and it is possible to display items with different sizes. The implementation of this part is located in the files ibitemdelegate.hpp and ibitemdelegate.cpp.
The goal for showing or hiding of section labels is closely related to the QListView data/items. For the realizion a so-called model (QAbstractItemModel) is necessary which is used by a QAbstractItemView to display items. It manages and prepares the displaying data. The classes of QAbstractItemView are only responsible for the rendering of the items. A detailed overview of that can be found in the Qt Documentation. A QListView instance can only handle 1-dimensional models or one specific column of a multidimensional model.
In case of the project, it is advantageous to organize the data in a 2-dimensional structure consisting of section items (IBImageListSectionItem) and images items (IBImageListImageItem) that stored in a main list (IBImageListSectionList). This simply helps to achieve the stated goals. The image items contains all image data (path, size, thumbnail, last modifed date and so on) and are stored in a list of the section items. The section items, in turn, are only consists of an ID and the list of image items. The main list finally stores and manages the section items with its image items and transforms the 2-dimensional data in 1-dimensional data. The tasks of the project model (IBImageListModel) are to populate the structure, to invoke its managment and to interface the data to the QListView instances.
If no section labels are to be displayed, the structure contains only one section item with an empty ID and all image items.
The item property of having different sizes, described in section Customize items, allows displaying section and image items. Section items are span the entired width of the view and must resize when the view is resized. The image items have a static size.
Sorting the different parts is very simple with the described structure. The class IBImageListSectionItem sorts the image items and the class IBImageListSectionList sorts the sections.
In Addition, the model class initialize a thread instance of class (IBThumbnailLoader), that loads the thumbnails of the image items. This approach allows a nonblocking use of the resulting application.
The implementation of this part is located in the files ibimagelistmodel.hpp and ibimagelistmodel.hpp.
git clone https://github.com/pmfoss/simpleimagebrowser
cd simpleimagebrowser
qmake
make
./simpleimagebrowser
BSD-3-Clause license