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POQLabel showing an image inside a QScrollArea
 

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    <p>I've successfully implemented a Image Viewer (for DICOM) in Qt. I can see the image and I can zoom in and out correctly.</p> <p>Now, I want to see scroll bars if the image is too big to show when I zoom in.</p> <p>I've used the UI. I placed a <strong>QScrollArea</strong>. Inside, the <strong>QLabel</strong>. The <em>verticalScrollBarPolicy</em> is <em>ScrollBarAsNeeded</em>. The <em>horizontalScrollBarPolicy</em> is <em>ScrollBarAsNeeded</em>.</p> <p>The problem is: it doesn't work. I zoom in, but no scrollbar appears.</p> <h1>Second try: using a layout inside the QScrollArea.</h1> <p>So now there's a <strong>QWidget</strong> between the QScrollArea and the QLabel: a horizontal layout. Opened the same image, now I can see a vertical scroll bar on the right. The image is streched from left to right. When I zoom the image gets its correct proportion.</p> <p>BUT... I zoom out and the scroll bar is the same, even if I can see the whole image. The horizontal scroll bar never appears.</p> <p>Resizing the QLabel doesn't seem to affect. But if I resize the QScrollArea (resizing the main window) the horizontal scroll bar appears.</p> <h1>I've been checking some numbers:</h1> <h2>In the QScrollArea</h2> <ul> <li>Its size changes: below 599 width (why this number? I can't see it anywhere) the horizontal bar appears.</li> <li><em>sizeHint()</em> always returns the same values: 33x41</li> </ul> <h2>In the QLabel</h2> <ul> <li>The dimensions change, but that doesn't affect.</li> <li><em>sizeHint()</em> always returns the same values: 560x1558</li> </ul> <p>Here is the code in XML from the UI designer:</p> <pre><code>&lt;widget class="QWidget" name="centralWidget"&gt; &lt;property name="autoFillBackground"&gt; &lt;bool&gt;false&lt;/bool&gt; &lt;/property&gt; &lt;layout class="QVBoxLayout" name="verticalLayout"&gt; &lt;property name="margin"&gt; &lt;number&gt;0&lt;/number&gt; &lt;/property&gt; &lt;item&gt; &lt;widget class="QScrollArea" name="scrollArea"&gt; &lt;property name="widgetResizable"&gt; &lt;bool&gt;true&lt;/bool&gt; &lt;/property&gt; &lt;property name="alignment"&gt; &lt;set&gt;Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop&lt;/set&gt; &lt;/property&gt; &lt;widget class="QWidget" name="scrollAreaWidgetContents"&gt; &lt;property name="geometry"&gt; &lt;rect&gt; &lt;x&gt;0&lt;/x&gt; &lt;y&gt;0&lt;/y&gt; &lt;width&gt;637&lt;/width&gt; &lt;height&gt;649&lt;/height&gt; &lt;/rect&gt; &lt;/property&gt; &lt;layout class="QHBoxLayout" name="horizontalLayout_2"&gt; &lt;item&gt; &lt;widget class="QLabel" name="miImagen"&gt; &lt;property name="sizePolicy"&gt; &lt;sizepolicy hsizetype="Preferred" vsizetype="Preferred"&gt; &lt;horstretch&gt;0&lt;/horstretch&gt; &lt;verstretch&gt;0&lt;/verstretch&gt; &lt;/sizepolicy&gt; &lt;/property&gt; &lt;property name="autoFillBackground"&gt; &lt;bool&gt;true&lt;/bool&gt; &lt;/property&gt; &lt;property name="scaledContents"&gt; &lt;bool&gt;true&lt;/bool&gt; &lt;/property&gt; &lt;property name="alignment"&gt; &lt;set&gt;Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop&lt;/set&gt; &lt;/property&gt; &lt;/widget&gt; &lt;/item&gt; &lt;/layout&gt; &lt;/widget&gt; &lt;/widget&gt; &lt;/item&gt; &lt;/layout&gt; &lt;/widget&gt; </code></pre> <p>What am I missing? Thank you.</p>
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    1. COWhat do you mean 'zoom in'? The scroll bars will only appear if the `QLabel` becomes larger than the `QScrollArea`.
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    2. COYes, when I zoom in, the QLabel becomes larger because I get more detail in that image. The image grows.
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    3. COPlease post the code where you create and set the properties for the widgets.
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