Applications: Add a very simple PDFViewer

Userland/Applications/PDFViewer/PDFViewer.cpp

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+/*
+ * Copyright (c) 2021, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "PDFViewer.h"
+#include <LibGUI/Action.h>
+#include <LibGUI/Painter.h>
+#include <LibPDF/Renderer.h>
+
+PDFViewer::PDFViewer()
+{
+    set_should_hide_unnecessary_scrollbars(true);
+    set_focus_policy(GUI::FocusPolicy::StrongFocus);
+    set_scrollbars_enabled(true);
+}
+
+PDFViewer::~PDFViewer()
+{
+}
+
+void PDFViewer::set_document(RefPtr<PDF::Document> document)
+{
+    m_document = document;
+    m_current_page_index = document->get_first_page_index();
+    update();
+}
+
+RefPtr<Gfx::Bitmap> PDFViewer::get_rendered_page(u32 index)
+{
+    auto existing_rendered_page = m_rendered_pages.get(index);
+    if (existing_rendered_page.has_value())
+        return existing_rendered_page.value();
+
+    auto rendered_page = render_page(m_document->get_page(index));
+    m_rendered_pages.set(index, rendered_page);
+    return rendered_page;
+}
+
+void PDFViewer::paint_event(GUI::PaintEvent& event)
+{
+    GUI::Frame::paint_event(event);
+
+    GUI::Painter painter(*this);
+    painter.add_clip_rect(widget_inner_rect());
+    painter.add_clip_rect(event.rect());
+    painter.fill_rect(event.rect(), Color(0x80, 0x80, 0x80));
+
+    if (!m_document)
+        return;
+
+    painter.translate(frame_thickness(), frame_thickness());
+    painter.translate(-horizontal_scrollbar().value(), -vertical_scrollbar().value());
+
+    auto page = get_rendered_page(m_current_page_index);
+
+    auto total_width = width() - frame_thickness() * 2;
+    auto total_height = height() - frame_thickness() * 2;
+    auto bitmap_width = page->width();
+    auto bitmap_height = page->height();
+
+    Gfx::IntPoint p { (total_width - bitmap_width) / 2, (total_height - bitmap_height) / 2 };
+
+    painter.blit(p, *page, page->rect());
+}
+
+void PDFViewer::mousewheel_event(GUI::MouseEvent& event)
+{
+    if (event.wheel_delta() > 0) {
+        if (m_current_page_index < m_document->get_page_count() - 1)
+            m_current_page_index++;
+    } else if (m_current_page_index > 0) {
+        m_current_page_index--;
+    }
+    update();
+}
+
+RefPtr<Gfx::Bitmap> PDFViewer::render_page(const PDF::Page& page)
+{
+    float page_width = page.media_box.upper_right_x - page.media_box.lower_left_x;
+    float page_height = page.media_box.upper_right_y - page.media_box.lower_left_y;
+    float page_scale_factor = page_height / page_width;
+
+    float width = 300.0f;
+    float height = width * page_scale_factor;
+    auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, { width, height });
+
+    PDF::Renderer::render(*m_document, page, bitmap);
+    return bitmap;
+}