基于lvgl v7.11.0

一、關于硬件加速

LVGL提供了一些GPU的硬件加速接口 lv_hal_disp.h
可以在lv_conf.h 中將宏打開。

#define LV_USE_GPU 1 /*Only enables `gpu_fill_cb` and `gpu_blend_cb` in the disp. drv- */

相關接口如下：

/** MANDATORY: Write the internal buffer (VDB) to the display. 'lv_disp_flush_ready()' has to be* called when finished */void (*flush_cb)(struct _disp_drv_t * disp_drv, const lv_area_t * area, lv_color_t * color_p);/** OPTIONAL: Extend the invalidated areas to match with the display drivers requirements* E.g. round `y` to, 8, 16 ..) on a monochrome display*/void (*rounder_cb)(struct _disp_drv_t * disp_drv, lv_area_t * area);/** OPTIONAL: Set a pixel in a buffer according to the special requirements of the display* Can be used for color format not supported in LittelvGL. E.g. 2 bit -> 4 gray scales* @note Much slower then drawing with supported color formats. */void (*set_px_cb)(struct _disp_drv_t * disp_drv, uint8_t * buf, lv_coord_t buf_w, lv_coord_t x, lv_coord_t y,lv_color_t color, lv_opa_t opa);/** OPTIONAL: Called after every refresh cycle to tell the rendering and flushing time + the* number of flushed pixels */void (*monitor_cb)(struct _disp_drv_t * disp_drv, uint32_t time, uint32_t px);/** OPTIONAL: Called periodically while lvgl waits for operation to be completed.* For example flushing or GPU* User can execute very simple tasks here or yield the task */void (*wait_cb)(struct _disp_drv_t * disp_drv);/** OPTIONAL: Called when lvgl needs any CPU cache that affects rendering to be cleaned */void (*clean_dcache_cb)(struct _disp_drv_t * disp_drv);/** OPTIONAL: called to wait while the gpu is working */void (*gpu_wait_cb)(struct _disp_drv_t * disp_drv);#if LV_USE_GPU/** OPTIONAL: Blend two memories using opacity (GPU only)*/void (*gpu_blend_cb)(struct _disp_drv_t * disp_drv, lv_color_t * dest, const lv_color_t * src, uint32_t length,lv_opa_t opa);/** OPTIONAL: Fill a memory with a color (GPU only)*/void (*gpu_fill_cb)(struct _disp_drv_t * disp_drv, lv_color_t * dest_buf, lv_coord_t dest_width,const lv_area_t * fill_area, lv_color_t color); #endif

flush_cb 雙framebuffer切換
gpu_fill_cb 區域色彩填充
gpu_blend_cb 區域 alpha 操作

所以就是說你要實現cpu自帶的硬件加速比如海思的tde等需要自己實現上述的接口。可以參考在lv_port_disp.c 中實現。

二、關于雙framebuffer

fb一般都有雙buffer的機制，用于前臺顯示后臺繪制，當后臺繪制完成后lcd控制器切換到后臺buffer顯示，這樣繪制過程就不會讓界面顯示出現撕裂及閃爍的情況。
lvgl提供了雙buffer的模式。lv_port_disp.c

void lv_port_disp_init(void)/* 3. Create TWO screen-sized buffer:* Similar to 2) but the buffer have to be screen sized. When LVGL is ready it will give the* whole frame to display. This way you only need to change the frame buffer's address instead of* copying the pixels.* *//* Example for 3) */static lv_disp_buf_t draw_buf_dsc_3;static lv_color_t draw_buf_3_1[LV_HOR_RES_MAX * LV_VER_RES_MAX]; /*A screen sized buffer*/static lv_color_t draw_buf_3_2[LV_HOR_RES_MAX * LV_VER_RES_MAX]; /*An other screen sized buffer*/lv_disp_buf_init(&draw_buf_dsc_3, draw_buf_3_1, draw_buf_3_2, LV_HOR_RES_MAX * LV_VER_RES_MAX); /*Initialize the display buffer*/disp_drv.buffer = &draw_buf_dsc_3;disp_drv.flush_cb = disp_flush; //注冊硬件加速函數#if LV_USE_GPU/*Optionally add functions to access the GPU. (Only in buffered mode, LV_VDB_SIZE != 0)*//*Blend two color array using opacity*/disp_drv.gpu_blend_cb = gpu_blend;/*Fill a memory array with a color*/disp_drv.gpu_fill_cb = gpu_fill; #endif/*Finally register the driver*/lv_disp_drv_register(&disp_drv);

注意注釋部分

/* 3. Create TWO screen-sized buffer:
* Similar to 2) but the buffer have to be screen sized. When LVGL is ready it will give the
* whole frame to display. This way you only need to change the frame buffer’s address instead of
* copying the pixels.
* */
lvgl在拿到這兩個buffer的時候會在后臺的buffer上直接繪制，等待繪制成功后再切換buffer，切換動作在flush_cb 上完成，然后再同步前后臺更新的內容，保存兩個buffer間的圖像同步。lvgl的繪制流程是上述這樣，v8.0換了一種繪制模式，就是小區域的ui更新將引發整個screen的更新也就是每次都繪制整個界面的obj，所以這時候就不用做雙buffer間的圖像同步了。
這兩種刷新方式我覺得還是第一中比較方便。因為做圖像同步的過程可以加入硬件加速。這樣整體流程會快很多。相較于第二種更新方式，每次都是刷整個screen耗時較多且沒有地方能加入加速。

關于v8.0注意在移植的時候如果你開了雙buffer的模式記得使能disp_drv.full_refresh = 1.

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