windows_screenshot.ua

# This works... but cant read the output array in the final step! :(

# Experimental!
UserLib ← &ffi ⊂□"User32.dll"
GdiLib ← &ffi ⊂□"Gdi32.dll"
KernelLib ← &ffi ⊂□"Kernel32.dll"
MessageBoxA ← UserLib {"int" "MessageBoxA" "long" "const char*" "const char*" "unsigned int"}
# MessageBoxA {0 "Yes Please" "About to Take A Screenshot" 0}
GetSystemMetrics ← UserLib {"int" "GetSystemMetrics" "int"}
GetDeviceContext ← UserLib {"long long" "GetDC" "long"}
CreateCompatibleDeviceContext ← GdiLib {"long long" "CreateCompatibleDC" "long long"}
CreateCompatibleBitmap ← GdiLib {"long long" "CreateCompatibleBitmap" "int" "int" "int"}
ScreenSize ← ∵GetSystemMetrics [0 1] # Primary Screen Size
# struct BITMAPINFOHEADER{ [SIZE 320]
#     32 unsigned long DWORD      biSize;
#     32          long LONG       biWidth;
#     32          long LONG       biHeight;
#     16         short WORD       biPlanes;
#     16         short WORD       biBitCount;
#     32 unsigned long DWORD      biCompression;
#     32 unsigned long DWORD      biSizeImage;
#     32          long LONG       biXPelsPerMeter;
#     32          long LONG       biYPelsPerMeter;
#     32 unsigned long DWORD      biClrUsed;
#     32 unsigned long DWORD      biClrImportant;
# }
# struct BITMAPINFO{ [size 352]
#     320 BITMAPINFOHEADER    bmiHeader;
#     32  RGBQUAD             bmiColors[1];
# }
BITMAPINFO ← "{unsigned long; long; long; short; short; unsigned long; unsigned long; long; long; unsigned long; unsigned long; long}"

# gdi32.BitBlt(hdcMemory, 0, 0, w, h, hdcScreen, l, t, SRCCOPY)
BitBlt ← GdiLib {"long long" "BitBlt" "long long" "int" "int" "int" "int" "long long" "int" "int" "long"}
SelectObject ← GdiLib {"long long" "SelectObject" "long long" "long long"}
GetDIBits ← GdiLib {"int" "GetDIBits" "long long" "long long" "unsigned int" "unsigned int" "int*" ⊂BITMAPINFO"*" "unsigned int"}

Valid ← ≠0             # not NULL 
ValidGDI ← ≠4294967295 # not HGDI_ERROR

s ← GetDeviceContext 0
⍤ "Failed to get Screen Device Context" Valid s

m ← CreateCompatibleDeviceContext s
⍤ "Failed to CreateCompatibleDeviceContext" Valid m

b ← GdiLib {"long long" "CreateCompatibleBitmap" "int" "int" "int"} {m °[⊙⊙]ScreenSize}
⍤ "Failed to Create Bitmap" Valid b

# returns previously selected object handel if succesful
SelectObject {m b}
⍤ "Failed to Select Object" ↧⊃Valid ValidGDI

# returns 1 if successful
BitBlt {
  m               # [in] mem handel
  0 0             # [in] top left of destination rect
  °[⊙⊙]ScreenSize # [in] screen size
  s               #  [in] source device context
  0 0             # [in] top left of source rectangle
  52256}          # [in] opperation (SRCCOPY=52256)
⍤ "Failed to Blit" Valid

# returns the number of lines (image height) if successful, as well as the BITMAPINFO struct, and the data array
GetDIBits {
  m                     # [in] mem handel
  b                     # [in] bitmap
  0                     # [in] start
  ⊡1 ScreenSize         # [in] height
  × 0 ⇡ ×3 /×ScreenSize # [out] create an array big enough to read the result
  [
    # [in & out] BITMAPINFO struct
    350
    °[⊙⊙]ScreenSize
    1    # Planes ; always 1
    ×8 3 # Channel bitcount
    0    # compression BI_RGB
    0    # biSizeImage
    0    # biXPelsPerMeter
    0    # biYPelsPerMeter
    0    # biClrUsed
    0    # biClrImportant
    0  ] # bmiColors
  0}     # [in] usage DIB_RGB_COLORS
⍤ "Failed to Retrieve Result" ◇=⊢ ⇌ ScreenSize ⊢ .

# result is {1440 {40 2560 1440 1 24 0 11059200 0 0 0 0 0} 0}
# the first two elements are expected, the last element should be a massive array?