RasterLayer: Properly handle GUI updates when multiple canvas are displayed #59444
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ptitjano
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🪟 Windows buildsDownload Windows builds of this PR for testing. 🪟 Windows Qt6 buildsDownload Windows Qt6 builds of this PR for testing. |
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nyalldawson
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Nov 18, 2024
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Good approach, I like where this is going! 👍 |
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@nyalldawson This should be ready now. |
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nyalldawson
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Much cleaner, this is great! 💯 |
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Looks good 👍 This approach will be useful for MeshLayer as well. |
This will be used in the next commits to store the min-max values of a raster layer and report them to the main canvas.
This is similar to what is achieved in `QgsRasterLayer::refreshRendererIfNeeded()` to check if the renderer needs to be refresh according to an extent. It does not perform any refresh. It is not used at the moment. This will replace the logic to refresh a renderer in the following commits.
This is similar to what is achieved in `QgsRasterLayer::refreshRenderer()` to refresh the renderer according to an extent. Contrary to the first one, this method does not perform any GUI update or emit any signal. It is not used at the moment. This will replace the logic to refresh a renderer in the following commits.
This will be used in the next commit to refresh a renderer.
This replaces the existing logic in `QgsRasterLayerRenderer` which calls `QgsRasterLayer::refreshRendererIfNeeded()` to refresh the renderer associated `QgsRasterLayerRenderer` and the raster associated with `QgsRasterLayer`. It also makes GUI updates. With this approach, the following new logic is done: 1. `QgsRasterRenderer::needsRefresh()` is called to check if `rasterRenderer` needs to be updated. 2. If a refresh is needed, the new min/max values are computed by calling `QgsRasterLayer::computeMinMax()` 3. The min/max values are used to refresh `rasterRenderer` 4. The min/max values are stored in a `QgsRenderedLayerStatistics` and propagated to `QgisApp` 5. In QgisApp, `QgsRenderedLayerStatistics` is used to refresh the renderer of `QgsRasterLayer` and force a refresh of the style and the legend if the change comes from the main canvas.
This is not used anymore.
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nyalldawson
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Description
This fixes an issue mentioned by @nyalldawson in qgis/QGIS-Enhancement-Proposals#273
This occurs when the Min/Max settings is set in the renderer and multiple canvas are displayed. Indeed, in that case
QgsRasterLayerupdates the GUI (the renderer widget and the legend) multiple times when the rendered values are updated because each canvas causes a renderer update.This issue is fixed by removing the GUI update from the raster layer code. With this change, when the rendered values are updated, these statistics (min-max) are propagated to the canvas by the use of a
QgsRenderedItemDetails:QgsRenderedCalculatedResults. Then, only the main canvas is notified of this change and updates the GUI accordingly.