1.前言

在android 10.0的系统rom定制化开发工作中，在系统中recoverv的页面也是相关重要的一部分，在系统recovery ta升级等功能，都是需要recoverv功能的，在某些产品定制化中
在recovery的时候，发现居然旋转了180度，接下来分析下recovery关于屏幕显示方向的相关源码，来修改这个功能

2.recovery页面旋转180度问题的解决方案的核心类

     bootable/recovery/minui/include/minui/minui.hboottable/recovery/minui/graphics.cpp

3.recovery页面旋转180度问题的解决方案的核心功能分析和实现

recovery页面旋转180度问题的解决方案的核心功能实现中，Android10.0的Recovery中的相关系统源码中，recoverv是以bootablerecovery下的minui库作为基础，采用的是直接存取framebuffer的万式，来完成recovery中所需的各种UI的绘制。
在recoverv的源码中，跟ui显示相关的代码的大致结构为:
boottable/recovery/minui下resources.cpp，graphics.cpp
其中resources.cpp提供的api主要用于图片资源的读取和加载
graphics.cpp负责具体完成各类ui的绘制既然graphics.cpp是负责各类UI的绘制那么旋转方向的修改 就要从这里入手了。

   #include "graphics.h"#include <stdint.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <memory>#include <android-base/properties.h>#include "graphics_adf.h"#include "graphics_drm.h"#include "graphics_fbdev.h"#include "minui/minui.h"...int gr_measure(const GRFont* font, const char* s) {if (font == nullptr) {return -1;}return font->char_width * strlen(s);}int gr_font_size(const GRFont* font, int* x, int* y) {if (font == nullptr) {return -1;}*x = font->char_width;*y = font->char_height;return 0;}// Increments pixel pointer right, with current rotation.static void incr_x(uint32_t** p, int row_pixels) {if (rotation == GRRotation::LEFT) {*p = *p - row_pixels;} else if (rotation == GRRotation::RIGHT) {*p = *p + row_pixels;} else if (rotation == GRRotation::DOWN) {*p = *p - 1;} else {  // GRRotation::NONE*p = *p + 1;}}// Increments pixel pointer down, with current rotation.static void incr_y(uint32_t** p, int row_pixels) {if (rotation == GRRotation::LEFT) {*p = *p + 1;} else if (rotation == GRRotation::RIGHT) {*p = *p - 1;} else if (rotation == GRRotation::DOWN) {*p = *p - row_pixels;} else {  // GRRotation::NONE*p = *p + row_pixels;}}void gr_fill(int x1, int y1, int x2, int y2) {x1 += overscan_offset_x;y1 += overscan_offset_y;x2 += overscan_offset_x;y2 += overscan_offset_y;if (outside(x1, y1) || outside(x2 - 1, y2 - 1)) return;int row_pixels = gr_draw->row_bytes / gr_draw->pixel_bytes;uint32_t* p = PixelAt(gr_draw, x1, y1, row_pixels);uint8_t alpha = static_cast<uint8_t>(((gr_current & alpha_mask) >> 24));if (alpha > 0) {for (int y = y1; y < y2; ++y) {uint32_t* px = p;for (int x = x1; x < x2; ++x) {*px = pixel_blend(alpha, *px);incr_x(&px, row_pixels);}incr_y(&p, row_pixels);}}}int gr_init_font(const char* name, GRFont** dest) {GRFont* font = static_cast<GRFont*>(calloc(1, sizeof(*gr_font)));if (font == nullptr) {return -1;}int res = res_create_alpha_surface(name, &(font->texture));if (res < 0) {free(font);return res;}// The font image should be a 96x2 array of character images.  The// columns are the printable ASCII characters 0x20 - 0x7f.  The// top row is regular text; the bottom row is bold.font->char_width = font->texture->width / 96;font->char_height = font->texture->height / 2;*dest = font;return 0;}int gr_init() {// pixel_format needs to be set before loading any resources or initializing backends.std::string format = android::base::GetProperty("ro.minui.pixel_format", "");if (format == "ABGR_8888") {pixel_format = PixelFormat::ABGR;} else if (format == "RGBX_8888") {pixel_format = PixelFormat::RGBX;} else if (format == "BGRA_8888") {pixel_format = PixelFormat::BGRA;} else {pixel_format = PixelFormat::UNKNOWN;}int ret = gr_init_font("font", &gr_font);if (ret != 0) {printf("Failed to init font: %d, continuing graphic backend initialization without font file\n",ret);}auto backend = std::unique_ptr<MinuiBackend>{ std::make_unique<MinuiBackendAdf>() };gr_draw = backend->Init();if (!gr_draw) {backend = std::make_unique<MinuiBackendDrm>();gr_draw = backend->Init();}if (!gr_draw) {backend = std::make_unique<MinuiBackendFbdev>();gr_draw = backend->Init();}if (!gr_draw) {return -1;}gr_backend = backend.release();int overscan_percent = android::base::GetIntProperty("ro.minui.overscan_percent", 0);overscan_offset_x = gr_draw->width * overscan_percent / 100;overscan_offset_y = gr_draw->height * overscan_percent / 100;gr_flip();gr_flip();if (!gr_draw) {printf("gr_init: gr_draw becomes nullptr after gr_flip\n");return -1;}std::string rotation_str =android::base::GetProperty("ro.minui.default_rotation", "ROTATION_NONE");if (rotation_str == "ROTATION_RIGHT") {gr_rotate(GRRotation::RIGHT);} else if (rotation_str == "ROTATION_DOWN") {gr_rotate(GRRotation::DOWN);} else if (rotation_str == "ROTATION_LEFT") {gr_rotate(GRRotation::LEFT);} else {  // "ROTATION_NONE" or unknown stringgr_rotate(GRRotation::NONE);}rotation = GRRotation::RIGHT;//add codeif (gr_draw->pixel_bytes != 4) {printf("gr_init: Only 4-byte pixel formats supported\n");}return 0;}void gr_rotate(GRRotation rot) {rotation = rot;}

recoverv页面旋转180度问题的解决方案的核心功能实现中，从graphics.cpp中的上述源码中,可以看出 r get width (const GRSurtace?surface)是获取屏幕的宽度
gr get height(const GRSurface* surface) 获取屏幕的高度
gr init font(const char* name.GRFont** dest) 获取字体大小
gr init() 主要是设置RGB 和 屏幕旋转方向,gr cear()清除一些绘制屏幕参数，重新绘制屏幕显示相关的参数接下来看下相关的设置recoverv的方向的相关代码的分析
gr rotate(DEFAULT ROTATION):
在gr init()的方法中中的gr rotate(DEFAULT ROTATION):设置屏幕的方向为默认方向而在minui.h中定义了recoverv方向的相关参数，如下

enum GRRotation {ROTATION_NONE = 0,ROTATION_RIGHT = 1,//90ROTATION_DOWN = 2,//180ROTATION_LEFT = 3,//270};

recovev页面旋转180度问题的解决方案的核心功能实现中，根据GRRotation 的相关参数可以得知，ROTATION RIGHT就是屏幕旋转90度，而ROTATION DOWN就是屏幕旋转180度，而ROTATION LEFT就是屏幕旋转270度，
所以设置横屏上下翻转就需要把屏幕方向修改为ROTATION LEFT就可以了具体修改为:

int gr_init() {....std::string rotation_str =android::base::GetProperty("ro.minui.default_rotation", "ROTATION_NONE");if (rotation_str == "ROTATION_RIGHT") {gr_rotate(GRRotation::RIGHT);} else if (rotation_str == "ROTATION_DOWN") {gr_rotate(GRRotation::DOWN);} else if (rotation_str == "ROTATION_LEFT") {gr_rotate(GRRotation::LEFT);} else { // "ROTATION_NONE" or unknown stringgr_rotate(GRRotation::NONE);}+ rotation = GRRotation::LEFT;//add code....}

recover页面旋转180度问题的解决方案的核心功能实现中，在上述的graphics.cpp中的上述源码中分析得知，在gr init) 主要是设置RGB和 屏幕旋转方向，所以就是根据返回的
rotation的值来判断当前屏幕的旋转方向的，所以通过上述的修改方法，在gr init()
增加rotation = GRRotation:LEFT://add code来作为当前屏幕的旋转方法，就确保旋转180度，就是实现了功能要求