From 58112b1e251c03b0a72511508712f9a67ce84d25 Mon Sep 17 00:00:00 2001
From: Rhys Weatherley <rhys.weatherley@nokia.com>
Date: Thu, 7 Jan 2010 08:57:54 +1000
Subject: Add QImage::constBits() and QImage::constScanLine()

QImage::bits() and QImage::scanLine() can create deep copies
if the QImage is not const.  The constBits() and constScanLine()
functions make things more explicit and less error-prone.

Reviewed-by: Daniel Pope
---
 src/gui/image/qimage.cpp | 40 ++++++++++++++++++++++++++++++++++++++--
 src/gui/image/qimage.h   |  2 ++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index ec8dd88..fc1107d 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -1832,7 +1832,7 @@ void QImage::setColor(int i, QRgb c)
     qAlpha() to access the pixels.
 
     \sa bytesPerLine(), bits(), {QImage#Pixel Manipulation}{Pixel
-    Manipulation}
+    Manipulation}, constScanLine()
 */
 uchar *QImage::scanLine(int i)
 {
@@ -1862,6 +1862,28 @@ const uchar *QImage::scanLine(int i) const
 
 
 /*!
+    Returns a pointer to the pixel data at the scanline with index \a
+    i. The first scanline is at index 0.
+
+    The scanline data is aligned on a 32-bit boundary.
+
+    Note that QImage uses \l{Implicit Data Sharing} {implicit data
+    sharing}, but this function does \e not perform a deep copy of the
+    shared pixel data, because the returned data is const.
+
+    \sa scanLine(), constBits()
+    \since 4.7
+*/
+const uchar *QImage::constScanLine(int i) const
+{
+    if (!d)
+        return 0;
+
+    Q_ASSERT(i >= 0 && i < height());
+    return d->data + i * d->bytes_per_line;
+}
+
+/*!
     Returns a pointer to the first pixel data. This is equivalent to
     scanLine(0).
 
@@ -1870,7 +1892,7 @@ const uchar *QImage::scanLine(int i) const
     data, thus ensuring that this QImage is the only one using the
     current return value.
 
-    \sa scanLine(), byteCount()
+    \sa scanLine(), byteCount(), constBits()
 */
 uchar *QImage::bits()
 {
@@ -1898,6 +1920,20 @@ const uchar *QImage::bits() const
 }
 
 
+/*!
+    Returns a pointer to the first pixel data.
+
+    Note that QImage uses \l{Implicit Data Sharing} {implicit data
+    sharing}, but this function does \e not perform a deep copy of the
+    shared pixel data, because the returned data is const.
+
+    \sa bits(), constScanLine()
+    \since 4.7
+*/
+const uchar *QImage::constBits() const
+{
+    return d ? d->data : 0;
+}
 
 /*!
     \fn void QImage::reset()
diff --git a/src/gui/image/qimage.h b/src/gui/image/qimage.h
index ce7f450..4e74c0e 100644
--- a/src/gui/image/qimage.h
+++ b/src/gui/image/qimage.h
@@ -182,6 +182,7 @@ public:
 
     uchar *bits();
     const uchar *bits() const;
+    const uchar *constBits() const;
 #ifdef QT_DEPRECATED
     QT_DEPRECATED int numBytes() const;
 #endif
@@ -189,6 +190,7 @@ public:
 
     uchar *scanLine(int);
     const uchar *scanLine(int) const;
+    const uchar *constScanLine(int) const;
     int bytesPerLine() const;
 
     bool valid(int x, int y) const;
-- 
cgit v0.12