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Let's create an app that can actually handle input from user.
To do this we will need `ReadKeyStroke` function:
```
EFI_SIMPLE_TEXT_INPUT_PROTOCOL.ReadKeyStroke()
Summary:
Reads the next keystroke from the input device.
Prototype:
typedef
EFI_STATUS
(EFIAPI *EFI_INPUT_READ_KEY) (
IN EFI_SIMPLE_TEXT_INPUT_PROTOCOL *This,
OUT EFI_INPUT_KEY *Key
);
Parameters:
This A pointer to the EFI_SIMPLE_TEXT_INPUT_PROTOCOL instance.
Key A pointer to a buffer that is filled in with the keystroke information
for the key that was pressed.
Description:
The ReadKeyStroke() function reads the next keystroke from the input device.
Status Codes Returned:
EFI_SUCCESS The keystroke information was returned.
EFI_NOT_READY There was no keystroke data available.
EFI_DEVICE_ERROR The keystroke information was not returned due to hardware errors.
```
The `EFI_INPUT_KEY` function is defined like this:
```
typedef struct {
UINT16 ScanCode;
CHAR16 UnicodeChar;
} EFI_INPUT_KEY;
```
Create `InteractiveApp` with the following code:
```
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiLib.h>
EFI_STATUS
EFIAPI
UefiMain (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable
)
{
UINTN Index;
EFI_INPUT_KEY Key;
Print(L"Try to guess the secret symbol!\n");
Print(L"To quit press 'q'\n");
while(TRUE) {
gBS->WaitForEvent(1, &(gST->ConIn->WaitForKey), &Index);
gST->ConIn->ReadKeyStroke(gST->ConIn, &Key);
Print(L"ScanCode = %04x, UnicodeChar = %04x (%c)\n", Key.ScanCode, Key.UnicodeChar, Key.UnicodeChar);
if (Key.UnicodeChar == 'k') {
Print(L"Correct!\n");
break;
} else if (Key.UnicodeChar == 'q') {
Print(L"Bye!\n");
break;
} else {
Print(L"Wrong!\n");
}
}
gST->ConIn->Reset(gST->ConIn, FALSE);
return EFI_SUCCESS;
}
```
The code is pretty simple, so I hope no detailed explanation is needed.
App asks for the secret symbol and loops until user presses the correct one ('k'), or presses 'q'.
```
FS0:\> InteractiveApp.efi
Try to guess the secret symbol!
To quit press 'q'
ScanCode = 0000, UnicodeChar = 0066 (f)
Wrong!
ScanCode = 0000, UnicodeChar = 0074 (t)
Wrong!
ScanCode = 0000, UnicodeChar = 0073 (s)
Wrong!
ScanCode = 0000, UnicodeChar = 0069 (i)
Wrong!
ScanCode = 0000, UnicodeChar = 0061 (a)
Wrong!
ScanCode = 0000, UnicodeChar = 006E (n)
Wrong!
ScanCode = 0000, UnicodeChar = 006B (k)
Correct!
FS0:\>
```
With this app you can also look at how special keys are handled.
This is the output from "PageUp" key:
```
ScanCode = 0017, UnicodeChar = 0000 ( )
Wrong!
ScanCode = 0000, UnicodeChar = 005B ([)
Wrong!
ScanCode = 0000, UnicodeChar = 0035 (5)
Wrong!
ScanCode = 0000, UnicodeChar = 007E (~)
Wrong!
```
|
