GFXcanvas: Allow subclass to take charge of buffer allocations #465
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In Adafruit_dvhstx, the low level driver takes charge of the framebuffer allocations. Consequently, any allocation by the GFXcanvas class would be an unused waste of memory. Introduce a new constructor parameter `bool allocate_buffer=true`. The default preserves the old behavior of allocating the buffer in the constructor and freeing it in the destructor, while passing in `false` skips buffer allocation & freeing. In this case, the subclass must allocate the buffer before the first drawing operation (such as in its constructor or begin method), and free it in its own destructor or end method. The subclass can also freely change the buffer pointer at runtime, for instance in a swap method if the underlying framebuffer is double-buffered.
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I may need some help with this as there are clang-format changes in files I didn't touch and that I don't reproduce locally (with debian stable running Debian clang-format version 14.0.6). I'm not sure what version of clang-format is being used by ci... |
This runs version 19.1.7: uvx clang-format -i *.cpp *.h the changes look similar to what was shown during CI
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ping @ladyada this PR will be a requirement for the HSTX lib I'm working on |
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ladyada
approved these changes
Feb 19, 2025
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In Adafruit_dvhstx, the low level driver takes charge of the framebuffer allocations. Consequently, any allocation by the GFXcanvas class would be an unused waste of memory.
Introduce a new constructor parameter
bool allocate_buffer=true. The default preserves the old behavior of allocating the buffer in the constructor and freeing it in the destructor, while passing infalseskips buffer allocation & freeing.In this case, the subclass must allocate the buffer before the first drawing operation (such as in its constructor or begin method), and free it in its own destructor or end method.
The subclass can also freely change the buffer pointer at runtime, for instance in a swap method if the underlying framebuffer is double-buffered.
Closes: #464