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| author | jacqueline <me@jacqueline.id.au> | 2024-06-12 17:54:40 +1000 |
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| committer | jacqueline <me@jacqueline.id.au> | 2024-06-12 17:54:40 +1000 |
| commit | 64bd9053a25297f7a442ca831c7da5b44bd33f84 (patch) | |
| tree | a90c6cad25a12028302ab1a5334510fba0229bae /lib/lvgl/docs/porting/gpu.md | |
| parent | 611176ed667c4ed7ee9f609e958f9404f4aee91d (diff) | |
| download | tangara-fw-64bd9053a25297f7a442ca831c7da5b44bd33f84.tar.gz | |
Update LVGL to v9.1.0
Diffstat (limited to 'lib/lvgl/docs/porting/gpu.md')
| -rw-r--r-- | lib/lvgl/docs/porting/gpu.md | 198 |
1 files changed, 0 insertions, 198 deletions
diff --git a/lib/lvgl/docs/porting/gpu.md b/lib/lvgl/docs/porting/gpu.md deleted file mode 100644 index d09613ad..00000000 --- a/lib/lvgl/docs/porting/gpu.md +++ /dev/null @@ -1,198 +0,0 @@ -# Add custom GPU -LVGL has a flexible and extendable draw pipeline. You can hook it to do some rendering with a GPU or even completely replace the built-in software renderer. - -## Draw context -The core structure of drawing is `lv_draw_ctx_t`. -It contains a pointer to a buffer where drawing should happen and a couple of callbacks to draw rectangles, texts, and other primitives. - -### Fields -`lv_draw_ctx_t` has the following fields: -- `void * buf` Pointer to a buffer to draw into -- `lv_area_t * buf_area` The position and size of `buf` (absolute coordinates) -- `const lv_area_t * clip_area` The current clip area with absolute coordinates, always the same or smaller than `buf_area`. All drawings should be clipped to this area. -- `void (*draw_rect)()` Draw a rectangle with shadow, gradient, border, etc. -- `void (*draw_arc)()` Draw an arc -- `void (*draw_img_decoded)()` Draw an (A)RGB image that is already decoded by LVGL. -- `lv_res_t (*draw_img)()` Draw an image before decoding it (it bypasses LVGL's internal image decoders) -- `void (*draw_letter)()` Draw a letter -- `void (*draw_line)()` Draw a line -- `void (*draw_polygon)()` Draw a polygon -- `void (*draw_bg)()` Replace the buffer with a rect without decoration like radius or borders. -- `void (*wait_for_finish)()` Wait until all background operation are finished. (E.g. GPU operations) -- `void * user_data` Custom user data for arbitrary purpose - -(For the sake of simplicity the parameters of the callbacks are not shown here.) - -All `draw_*` callbacks receive a pointer to the current `draw_ctx` as their first parameter. Among the other parameters there is a descriptor that tells what to draw, -e.g. for `draw_rect` it's called [lv_draw_rect_dsc_t](https://github.com/lvgl/lvgl/blob/master/src/draw/lv_draw_rect.h), -for `lv_draw_line` it's called [lv_draw_line_dsc_t](https://github.com/lvgl/lvgl/blob/master/src/draw/lv_draw_line.h), etc. - -To correctly render according to a `draw_dsc` you need to be familiar with the [Boxing model](https://docs.lvgl.io/master/overview/coords.html#boxing-model) of LVGL and the meanings of the fields. The name and meaning of the fields are identical to name and meaning of the [Style properties](https://docs.lvgl.io/master/overview/style-props.html). - -### Initialization -The `lv_disp_drv_t` has 4 fields related to the draw context: -- `lv_draw_ctx_t * draw_ctx` Pointer to the `draw_ctx` of this display -- `void (*draw_ctx_init)(struct _lv_disp_drv_t * disp_drv, lv_draw_ctx_t * draw_ctx)` Callback to initialize a `draw_ctx` -- `void (*draw_ctx_deinit)(struct _lv_disp_drv_t * disp_drv, lv_draw_ctx_t * draw_ctx)` Callback to de-initialize a `draw_ctx` -- `size_t draw_ctx_size` Size of the draw context structure. E.g. `sizeof(lv_draw_sw_ctx_t)` - -When you ignore these fields, LVGL will set default values for callbacks and size in `lv_disp_drv_init()` based on the configuration in `lv_conf.h`. -`lv_disp_drv_register()` will allocate a `draw_ctx` based on `draw_ctx_size` and call `draw_ctx_init()` on it. - -However, you can overwrite the callbacks and the size values before calling `lv_disp_drv_register()`. -It makes it possible to use your own `draw_ctx` with your own callbacks. - - -## Software renderer -LVGL's built in software renderer extends the basic `lv_draw_ctx_t` structure and sets the draw callbacks. It looks like this: -```c -typedef struct { - /** Include the basic draw_ctx type*/ - lv_draw_ctx_t base_draw; - - /** Blend a color or image to an area*/ - void (*blend)(lv_draw_ctx_t * draw_ctx, const lv_draw_sw_blend_dsc_t * dsc); -} lv_draw_sw_ctx_t; -``` - -Set the draw callbacks in `draw_ctx_init()` like: -```c -draw_sw_ctx->base_draw.draw_rect = lv_draw_sw_rect; -draw_sw_ctx->base_draw.draw_letter = lv_draw_sw_letter; -... -``` - -### Blend callback -As you saw above the software renderer adds the `blend` callback field. It's a special callback related to how the software renderer works. -All draw operations end up in the `blend` callback which can either fill an area or copy an image to an area by considering an optional mask. - -The `lv_draw_sw_blend_dsc_t` parameter describes what and how to blend. It has the following fields: -- `const lv_area_t * blend_area` The area with absolute coordinates to draw on `draw_ctx->buf`. If `src_buf` is set, it's the coordinates of the image to blend. -- `const lv_color_t * src_buf` Pointer to an image to blend. If set, `color` is ignored. If not set fill `blend_area` with `color` -- `lv_color_t color` Fill color. Used only if `src_buf == NULL` -- `lv_opa_t * mask_buf` NULL if ignored, or an alpha mask to apply on `blend_area` -- `lv_draw_mask_res_t mask_res` The result of the previous mask operation. (`LV_DRAW_MASK_RES_...`) -- `const lv_area_t * mask_area` The area of `mask_buf` with absolute coordinates -- `lv_opa_t opa` The overall opacity -- `lv_blend_mode_t blend_mode` E.g. `LV_BLEND_MODE_ADDITIVE` - - -## Extend the software renderer - -### New blend callback - -Let's take a practical example: you would like to use your MCUs GPU for color fill operations only. - -As all draw callbacks call `blend` callback to fill an area in the end only the `blend` callback needs to be overwritten. - -First extend `lv_draw_sw_ctx_t`: -```c - -/*We don't add new fields, so just for clarity add new type*/ -typedef lv_draw_sw_ctx_t my_draw_ctx_t; - -void my_draw_ctx_init(lv_disp_drv_t * drv, lv_draw_ctx_t * draw_ctx) -{ - /*Initialize the parent type first */ - lv_draw_sw_init_ctx(drv, draw_ctx); - - /*Change some callbacks*/ - my_draw_ctx_t * my_draw_ctx = (my_draw_ctx_t *)draw_ctx; - - my_draw_ctx->blend = my_draw_blend; - my_draw_ctx->base_draw.wait_for_finish = my_gpu_wait; -} -``` - -After calling `lv_disp_draw_init(&drv)` you can assign the new `draw_ctx_init` callback and set `draw_ctx_size` to overwrite the defaults: -```c -static lv_disp_drv_t drv; -lv_disp_draw_init(&drv); -drv->hor_res = my_hor_res; -drv->ver_res = my_ver_res; -drv->flush_cb = my_flush_cb; - -/*New draw ctx settings*/ -drv->draw_ctx_init = my_draw_ctx_init; -drv->draw_ctx_size = sizeof(my_draw_ctx_t); - -lv_disp_drv_register(&drv); -``` - -This way when LVGL calls `blend` it will call `my_draw_blend` and we can do custom GPU operations. Here is a complete example: -```c -void my_draw_blend(lv_draw_ctx_t * draw_ctx, const lv_draw_sw_blend_dsc_t * dsc) -{ - /*Let's get the blend area which is the intersection of the area to fill and the clip area.*/ - lv_area_t blend_area; - if(!_lv_area_intersect(&blend_area, dsc->blend_area, draw_ctx->clip_area)) return; /*Fully clipped, nothing to do*/ - - /*Fill only non masked, fully opaque, normal blended and not too small areas*/ - if(dsc->src_buf == NULL && dsc->mask == NULL && dsc->opa >= LV_OPA_MAX && - dsc->blend_mode == LV_BLEND_MODE_NORMAL && lv_area_get_size(&blend_area) > 100) { - - /*Got the first pixel on the buffer*/ - lv_coord_t dest_stride = lv_area_get_width(draw_ctx->buf_area); /*Width of the destination buffer*/ - lv_color_t * dest_buf = draw_ctx->buf; - dest_buf += dest_stride * (blend_area.y1 - draw_ctx->buf_area->y1) + (blend_area.x1 - draw_ctx->buf_area->x1); - - /*Make the blend area relative to the buffer*/ - lv_area_move(&blend_area, -draw_ctx->buf_area->x1, -draw_ctx->buf_area->y1); - - /*Call your custom gou fill function to fill blend_area, on dest_buf with dsc->color*/ - my_gpu_fill(dest_buf, dest_stride, &blend_area, dsc->color); - } - /*Fallback: the GPU doesn't support these settings. Call the SW renderer.*/ - else { - lv_draw_sw_blend_basic(draw_ctx, dsc); - } -} -``` - -The implementation of wait callback is much simpler: -```c -void my_gpu_wait(lv_draw_ctx_t * draw_ctx) -{ - while(my_gpu_is_working()); - - /*Call SW renderer's wait callback too*/ - lv_draw_sw_wait_for_finish(draw_ctx); -} -``` - -### New rectangle drawer -If your MCU has a more powerful GPU that can draw e.g. rounded rectangles you can replace the original software drawer too. -A custom `draw_rect` callback might look like this: -```c -void my_draw_rect(lv_draw_ctx_t * draw_ctx, const lv_draw_rect_dsc_t * dsc, const lv_area_t * coords) -{ - if(lv_draw_mask_is_any(coords) == false && dsc->grad == NULL && dsc->bg_img_src == NULL && - dsc->shadow_width == 0 && dsc->blend_mode = LV_BLEND_MODE_NORMAL) - { - /*Draw the background*/ - my_bg_drawer(draw_ctx, coords, dsc->bg_color, dsc->radius); - - /*Draw the border if any*/ - if(dsc->border_width) { - my_border_drawer(draw_ctx, coords, dsc->border_width, dsc->border_color, dsc->border_opa) - } - - /*Draw the outline if any*/ - if(dsc->outline_width) { - my_outline_drawer(draw_ctx, coords, dsc->outline_width, dsc->outline_color, dsc->outline_opa, dsc->outline_pad) - } - } - /*Fallback*/ - else { - lv_draw_sw_rect(draw_ctx, dsc, coords); - } -} -``` - -`my_draw_rect` can fully bypass the use of `blend` callback if needed. - -## Fully custom draw engine - -For example if your MCU/MPU supports a powerful vector graphics engine you might use only that instead of LVGL's SW renderer. -In this case, you need to base the renderer on the basic `lv_draw_ctx_t` (instead of `lv_draw_sw_ctx_t`) and extend/initialize it as you wish. - |
