Minimal implementation of QImage.

Just enough to make the qt-tutorial for KDAB Training day work.

Author: LeonMatthesKDAB

crates/cxx-qt-lib-headers/include/gui/qimage.h

@@ -0,0 +1,31 @@
+// clang-format off
+// SPDX-FileCopyrightText: 2023 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// clang-format on
+// SPDX-FileContributor: Leon Matthes <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+#pragma once
+
+#ifdef CXX_QT_GUI_FEATURE
+
+#include <QtGui/QImage>
+
+#include "rust/cxx.h"
+
+namespace rust {
+
+// QImage has a move constructor, however it is basically trivial.
+template<>
+struct IsRelocatable<QImage> : ::std::true_type
+{
+};
+
+namespace cxxqtlib1 {
+using QImageFormat = QImage::Format;
+
+QImage
+qimageInitFromData(const QByteArray& data, const char* format);
+
+} // namespace cxxqtlib1
+} // namespace rust
+#endif

crates/cxx-qt-lib-headers/src/lib.rs

@@ -71,6 +71,8 @@ pub fn write_headers(directory: impl AsRef<Path>) {
             "qguiapplication.h",
         ),
         #[cfg(feature = "qt_gui")]
+        (include_str!("../include/gui/qimage.h"), "qimage.h"),
+        #[cfg(feature = "qt_gui")]
         (include_str!("../include/gui/qvector2d.h"), "qvector2d.h"),
         #[cfg(feature = "qt_gui")]
         (include_str!("../include/gui/qvector3d.h"), "qvector3d.h"),

crates/cxx-qt-lib/build.rs

@@ -158,6 +158,7 @@ fn main() {
             "core/qvector/qvector_qcolor",
             "gui/qcolor",
             "gui/qguiapplication",
+            "gui/qimage",
             "gui/qvector2d",
             "gui/qvector3d",
             "gui/qvector4d",
@@ -225,6 +226,7 @@ fn main() {
         cpp_files.extend([
             "gui/qcolor",
             "gui/qguiapplication",
+            "gui/qimage",
             "gui/qvector2d",
             "gui/qvector3d",
             "gui/qvector4d",

crates/cxx-qt-lib/src/core/mod.rs

@@ -5,6 +5,7 @@
 
 mod qbytearray;
 pub use qbytearray::QByteArray;
+pub use qbytearray::QByteArrayCursor;
 
 mod qcoreapplication;
 pub use qcoreapplication::QCoreApplication;

crates/cxx-qt-lib/src/core/qbytearray.rs

@@ -3,7 +3,10 @@
 //
 // SPDX-License-Identifier: MIT OR Apache-2.0
 use cxx::{type_id, ExternType};
-use std::mem::MaybeUninit;
+use std::{
+    io::{Cursor, Seek, Write},
+    mem::MaybeUninit,
+};
 
 #[cxx::bridge]
 mod ffi {
@@ -122,6 +125,97 @@ impl AsRef<[u8]> for QByteArray {
     }
 }
 
+/// A QByteArray cursor allows seeking inside a QByteArray
+/// and writing to it.
+/// Comparable with std::io::Cursor.
+pub struct QByteArrayCursor {
+    inner: QByteArray,
+    position: isize,
+}
+
+impl QByteArrayCursor {
+    /// Constructs a new QByteArrayCursor at location 0.
+    /// Like std::io::Cursor<Vec<u8>> this will overwrite
+    /// existing data in the QByteArray before starting to resize.
+    pub fn new(bytearray: QByteArray) -> Self {
+        Self {
+            inner: bytearray,
+            position: 0,
+        }
+    }
+
+    /// Returns a reference to the underlying QByteArray.
+    pub fn into_inner(self) -> QByteArray {
+        self.inner
+    }
+}
+
+/// Like the implementation of Cursor<Vec<u8>>, the Cursor<QByteArray>
+/// will overwrite existing data in the QByteArray.
+/// The QByteArray is resized as needed.
+impl Write for QByteArrayCursor {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        let length_after_append = buf.len() as isize + self.position;
+        let bytearray_length = self.inner.len();
+        if length_after_append > bytearray_length {
+            self.inner.resize(length_after_append);
+        }
+
+        let bytes = self.inner.as_mut_slice();
+
+        // If the resize operation failed, then we need to do additional
+        // error handling.
+        // Luckily we can just leave this up to the Cursor<&mut [u8]> implementation.
+        let mut bytes_cursor = Cursor::new(bytes);
+        bytes_cursor.set_position(self.position as u64);
+
+        bytes_cursor.write(buf).map(|bytes_written| {
+            self.position += bytes_written as isize;
+            bytes_written
+        })
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        // Nothing to flush, we always write everything
+        Ok(())
+    }
+}
+
+impl AsRef<QByteArray> for QByteArrayCursor {
+    fn as_ref(&self) -> &QByteArray {
+        &self.inner
+    }
+}
+
+impl Seek for QByteArrayCursor {
+    fn seek(&mut self, pos: std::io::SeekFrom) -> std::io::Result<u64> {
+        use std::io::{Error, ErrorKind, SeekFrom};
+        let (base_pos, offset) = match pos {
+            SeekFrom::Start(n) => (
+                0_usize,
+                n.try_into().map_err(|_err| {
+                    Error::new(
+                        ErrorKind::InvalidInput,
+                        "invalid seek to an overflowing position",
+                    )
+                })?,
+            ),
+            SeekFrom::End(n) => (self.inner.len() as usize, n),
+            SeekFrom::Current(n) => (self.position as usize, n),
+        };
+        match base_pos.checked_add_signed(offset as isize) {
+            Some(n) => {
+                self.position = (n as isize).min(self.inner.len());
+                Ok(self.position as u64)
+            }
+            None => Err(Error::new(
+                ErrorKind::InvalidInput,
+                "invalid seek to a negative or overflowing position",
+            )),
+        }
+    }
+}
+
 impl Clone for QByteArray {
     /// Constructs a copy of other.
     ///

crates/cxx-qt-lib/src/gui/mod.rs

@@ -17,3 +17,6 @@ pub use qvector3d::QVector3D;
 
 mod qvector4d;
 pub use qvector4d::QVector4D;
+
+mod qimage;
+pub use qimage::QImage;

crates/cxx-qt-lib/src/gui/qimage.cpp

@@ -0,0 +1,47 @@
+// clang-format off
+// SPDX-FileCopyrightText: 2023 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// clang-format on
+// SPDX-FileContributor: Leon Matthes <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+#ifdef CXX_QT_GUI_FEATURE
+
+#include "cxx-qt-lib/qimage.h"
+#include "../assertion_utils.h"
+
+// A QImage inherits from QPaintDevice.
+
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+// QPaintDevice in Qt5 contains two things:
+// 1. ushort painters; (due to the following field this has padding to make it
+// 64-bit long)
+// 2. QPaintDevicePrivate *reserved;
+// Then QImage adds an additional field:
+// 3. QImageData *d;
+// For a total of 3 pointers in length.
+// Because of the added v-table, it's a total of 4 pointers in size.
+assert_alignment_and_size(QImage,
+                          alignof(::std::size_t),
+                          sizeof(::std::size_t) * 4);
+#else
+// In Qt6 the QPaintDevice doesn't contain the `reserved` pointer, making it 1
+// pointer smaller
+assert_alignment_and_size(QImage,
+                          alignof(::std::size_t),
+                          sizeof(::std::size_t) * 3);
+#endif
+
+namespace rust {
+namespace cxxqtlib1 {
+
+QImage
+qimageInitFromData(const QByteArray& data, const char* format)
+{
+  return QImage::fromData(data, format);
+}
+
+}
+}
+
+#endif

crates/cxx-qt-lib/src/gui/qimage.rs

@@ -0,0 +1,76 @@
+// SPDX-FileCopyrightText: 2023 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// SPDX-FileContributor: Leon Matthes <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+use crate::QByteArray;
+use cxx::{type_id, ExternType};
+use std::{
+    ffi::{c_char, CString},
+    mem::MaybeUninit,
+};
+
+#[cxx::bridge]
+mod ffi {
+
+    unsafe extern "C++" {
+        include!("cxx-qt-lib/qbytearray.h");
+        type QByteArray = crate::QByteArray;
+
+        include!("cxx-qt-lib/qimage.h");
+        type QImage = super::QImage;
+
+        #[rust_name = "is_null"]
+        fn isNull(self: &QImage) -> bool;
+    }
+
+    #[namespace = "rust::cxxqtlib1"]
+    unsafe extern "C++" {
+        include!("cxx-qt-lib/common.h");
+
+        #[doc(hidden)]
+        #[rust_name = "qimage_drop"]
+        fn drop(image: &mut QImage);
+
+        #[doc(hidden)]
+        #[rust_name = "qimage_init_from_data"]
+        unsafe fn qimageInitFromData(data: &QByteArray, format: *const c_char) -> QImage;
+    }
+}
+
+#[repr(C)]
+pub struct QImage {
+    // Static checks on the C++ side ensure this is true.
+    // See qcolor.cpp
+    #[cfg(qt_version_major = "5")]
+    _data: MaybeUninit<[usize; 4]>,
+    #[cfg(qt_version_major = "6")]
+    _data: MaybeUninit<[usize; 3]>,
+}
+
+// Safety:
+//
+// Static checks on the C++ side to ensure the size & alignment is the same.
+unsafe impl ExternType for QImage {
+    type Id = type_id!("QImage");
+    type Kind = cxx::kind::Trivial;
+}
+
+impl Drop for QImage {
+    fn drop(&mut self) {
+        ffi::qimage_drop(self);
+    }
+}
+
+impl QImage {
+    pub fn from_data(data: &QByteArray, format: &str) -> Option<Self> {
+        let format = CString::new(format).ok()?;
+        let image = unsafe { ffi::qimage_init_from_data(data, format.as_ptr() as *const c_char) };
+
+        if !image.is_null() {
+            Some(image)
+        } else {
+            None
+        }
+    }
+}