我对创建efi应用程序是超级新手。我的目标是在efi中创建一个小型应用程序，在背景上显示一些文本。但是我一直坚持尝试在显示器上显示文本（伟大的是拥有一种自定义字体，但这在现阶段不是必须的）。我希望该应用程序（也）可以在苹果系统上运行（从USB引导）
如何找到有关EFI功能的优质文档？看起来很难找到好的例子，等等。
如何使用EFI在背景上显示文本？
这是我到目前为止所得到的。我使用图形协议将背景更改为颜色。如何在上面显示文本。输出字符串似乎不起作用。
#include "efibind.h"
#include "efidef.h"
#include "efidevp.h"
#include "eficon.h"
#include "efiapi.h"
#include "efierr.h"
#include "efiprot.h"
static EFI_GUID GraphicsOutputProtocolGUID = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
/**
* efi_main - The entry point for the EFI application
* @image: firmware-allocated handle that identifies the image
* @SystemTable: EFI system table
*/
EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *systemTable) {
EFI_BOOT_SERVICES *bs = systemTable->BootServices;
EFI_STATUS status;
EFI_GRAPHICS_OUTPUT_PROTOCOL *graphicsProtocol;
SIMPLE_TEXT_OUTPUT_INTERFACE *conOut = systemTable->ConOut;
EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *info;
UINTN SizeOfInfo, sWidth, sHeight;
status = bs->LocateProtocol(&GraphicsOutputProtocolGUID, NULL,
(void**)&graphicsProtocol);
if (EFI_ERROR(status) || graphicsProtocol == NULL) {
conOut->OutputString(conOut, L"Failed to init gfx!\r\n");
return status;
}
conOut->ClearScreen(conOut);
//Switch to current mode so gfx is started.
status = graphicsProtocol->SetMode(graphicsProtocol, graphicsProtocol->Mode->Mode);
if (EFI_ERROR(status)) {
conOut->OutputString(conOut, L"Failed to set default mode!\r\n");
return status;
}
EFI_GRAPHICS_OUTPUT_BLT_PIXEL p;
p.Red = 200;
p.Green = 77;
p.Blue = 13;
graphicsProtocol->QueryMode(graphicsProtocol, graphicsProtocol->Mode->Mode, &SizeOfInfo, &info);
sWidth = info->HorizontalResolution;
sHeight = info->VerticalResolution;
status = graphicsProtocol->Blt(graphicsProtocol, &p, EfiBltVideoFill, 0, 0, 0, 0, sWidth, sHeight, 0);
while (1) {
conOut->OutputString(conOut, L"Some text that I want to display\r\n");
bs->Stall(500000);
}
return EFI_SUCCESS;
}
答案 0 :(得分：0)
如果您专门针对MacEFI，则需要额外的协议调用以将控制台强制进入文本模式like this。
答案 1 :(得分：0)
UEFI支持图形输出。它还支持文本输出（这可能意味着输出到串行控制台，或文本呈现到图形控制台，或两者）。但是，没有一种可控的方式在它们之间进行交互。
为图形环境提供文本元素（BIOS配置菜单，GRUB）的应用程序通常使用自己的框架通过GRAPHICS_OUTPUT_PROTOCOL在图形控制台上绘制文本。
答案 2 :(得分：0)
这是使用LVGL中的字体模块的文本渲染器的简短示例（可以单独使用，替换 #include“ ../../ lv_conf.h” 在带有 #define USE_LV_FONT_DEJAVU_20 8 的lv_font.h文件中）和来自GRAPHICS_OUTPUT_PROTOCOL
的Blt方法#include <Uefi.h>
#include <Library\UefiLib.h>
#include <Protocol\GraphicsOutput.h>
#include "lv_font.h"
#define LETTER_SPACE 2
#define WAIT_SECONDS 10
#define FONT &lv_font_dejavu_20
static EFI_BOOT_SERVICES *gBS;
static EFI_RUNTIME_SERVICES *gRT;
static EFI_GRAPHICS_OUTPUT_PROTOCOL *gGOP = (EFI_GRAPHICS_OUTPUT_PROTOCOL *)NULL;
static EFI_GRAPHICS_OUTPUT_BLT_PIXEL gWhite = { 255,255,255,0 };
static void _util_render_glyph(UINT32 x, UINT32 y, CHAR8 letter)
{
UINT32 height;
UINT32 width;
UINT32 pm_x;
UINT32 pm_y;
UINT32 index;
const UINT8* bitmap;
EFI_GRAPHICS_OUTPUT_BLT_PIXEL *pixelmap;
if (gGOP == NULL) {
return;
}
height = lv_font_get_height(FONT);
width = lv_font_get_width(FONT, letter);
// glyph is not defined in this font
if (width == 0) {
return;
}
bitmap = lv_font_get_bitmap(FONT, letter);
// using 8 bpp for simplicity
if (EFI_ERROR(gBS->AllocatePool(EfiLoaderData, height * width * sizeof(*pixelmap), (VOID**)&pixelmap))) {
return;
}
gBS->SetMem((VOID*)pixelmap, height * width * sizeof(*pixelmap), 0);
// get the current content of the framebuffer to allow 'transparent' blt operations
gGOP->Blt(gGOP, pixelmap, EfiBltVideoToBltBuffer, x, y, 0, 0, width, height, 0);
for (pm_y = 0; pm_y < height; pm_y++) {
for (pm_x = 0; pm_x < width; pm_x++) {
index = width * pm_y + pm_x;
if (bitmap[index] > 200) {
pixelmap[index].Red = 0;
pixelmap[index].Blue = 0;
pixelmap[index].Green = 0;
pixelmap[index].Reserved = 0;
}
else if (bitmap[index] > 100) {
pixelmap[index].Red = 105;
pixelmap[index].Blue = 105;
pixelmap[index].Green = 105;
pixelmap[index].Reserved = 0;
}
}
}
gGOP->Blt(gGOP, pixelmap, EfiBltBufferToVideo, 0, 0, x, y, width, height, 0);
gBS->FreePool(pixelmap);
}
static void _util_render_text(UINT32 x, UINT32 y, const CHAR8 *string)
{
UINT32 index;
UINTN length;
UINT32 scr_w;
UINT32 scr_h;
UINT32 str_x;
UINT32 gly_w;
UINT32 gly_h;
if (string == NULL) {
return;
}
if (gGOP == NULL) {
return;
}
scr_w = gGOP->Mode->Info->HorizontalResolution;
scr_h = gGOP->Mode->Info->VerticalResolution;
length = AsciiStrnLenS(string, 32);
gly_h = lv_font_get_height(FONT);
// check if the string can be printed
if ((y + gly_h) > scr_h) {
return;
}
if (x > scr_w) {
return;
}
// print the string glyph by glyph
str_x = x;
for (index = 0; index < length; index++) {
// check if the glyph can be printed
gly_w = lv_font_get_width(FONT, string[index]);
if ((str_x + gly_w) > scr_w) {
break;
}
// print the glyph
_util_render_glyph(str_x, y, string[index]);
// calculate the position of the next glyph
str_x += gly_w + LETTER_SPACE;
}
}
static void _util_fill_screen(EFI_GRAPHICS_OUTPUT_BLT_PIXEL *color)
{
if (gGOP == NULL) {
return;
}
gGOP->Blt(gGOP, color, EfiBltVideoFill, 0, 0, 0, 0, gGOP->Mode->Info->HorizontalResolution, gGOP->Mode->Info->VerticalResolution, 0);
}
static void _util_wait(UINT32 seconds)
{
EFI_TIME time;
UINT8 current_second = 255;
UINT32 elapsed_seconds = 0;
//wait for some seconds
while (elapsed_seconds <= WAIT_SECONDS) {
if (!EFI_ERROR(gRT->GetTime(&time, (EFI_TIME_CAPABILITIES*)NULL))) {
if (current_second != time.Second) {
elapsed_seconds++;
current_second = time.Second;
}
}
else {
break;
}
CpuPause();
}
}
EFI_STATUS
EFIAPI
UefiMain(
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable)
{
EFI_STATUS eRc;
gBS = SystemTable->BootServices;
gRT = SystemTable->RuntimeServices;
eRc = gBS->LocateProtocol(
&gEfiGraphicsOutputProtocolGuid,
NULL,
(VOID**)&gGOP);
if (EFI_ERROR(eRc) || gGOP == NULL) {
return EFI_SUCCESS;
}
_util_fill_screen(&gWhite);
_util_render_text(0, 0, "HELLO WORLD!");
_util_wait(WAIT_SECONDS);
return EFI_SUCCESS;
}
我在PC和Mac上都对其进行了测试。使用LVGL网站上提供的工具，您可以使用所需的任何字体。