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PDFViewer: Allow zooming in and out + scrolling

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When holding ctrl and scrolling, the page will be zoomed in an out.
When zoomed in on a page, scrolling with move vertically up and down
the page (or horizontally if shift is being held).

In order to speed up zooming, zoomed bitmaps are cached per-page at
each distinct zoom level. This cache is cleared every 30 seconds to
prevent OOM problems.
This commit is contained in:
Matthew Olsson 2021-05-10 14:00:06 -07:00 • committed by Andreas Kling
parent d5f94aaa7b
commit c3c2121b57
2 changed files with 104 additions and 22 deletions
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92
Userland/Applications/PDFViewer/PDFViewer.cpp
View file

@ -14,27 +14,33 @@ PDFViewer::PDFViewer()
set_should_hide_unnecessary_scrollbars(true);
set_focus_policy(GUI::FocusPolicy::StrongFocus);
set_scrollbars_enabled(true);
}
PDFViewer::~PDFViewer()
{
start_timer(30'000);
}
void PDFViewer::set_document(RefPtr<PDF::Document> document)
{
m_document = document;
m_current_page_index = document->get_first_page_index();
m_zoom_level = initial_zoom_level;
m_rendered_page_list.clear();
m_rendered_page_list.ensure_capacity(document->get_page_count());
for (u32 i = 0; i < document->get_page_count(); i++)
m_rendered_page_list.unchecked_append(HashMap<u32, RefPtr<Gfx::Bitmap>>());
update();
}
RefPtr<Gfx::Bitmap> PDFViewer::get_rendered_page(u32 index)
{
auto existing_rendered_page = m_rendered_pages.get(index);
auto& rendered_page_map = m_rendered_page_list[index];
auto existing_rendered_page = rendered_page_map.get(m_zoom_level);
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);
rendered_page_map.set(m_zoom_level, rendered_page);
return rendered_page;
}
@ -50,39 +56,85 @@ void PDFViewer::paint_event(GUI::PaintEvent& event)
if (!m_document)
return;
auto page = get_rendered_page(m_current_page_index);
set_content_size(page->size());
painter.translate(frame_thickness(), frame_thickness());
painter.translate(-horizontal_scrollbar().value(), -vertical_scrollbar().value());
auto page = get_rendered_page(m_current_page_index);
int x = max(0, (width() - page->width()) / 2);
int y = max(0, (height() - page->height()) / 2);
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());
painter.blit({ x, y }, *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--;
bool scrolled_down = event.wheel_delta() > 0;
if (event.ctrl()) {
if (scrolled_down) {
zoom_out();
} else {
zoom_in();
}
} else {
auto& scrollbar = event.shift() ? horizontal_scrollbar() : vertical_scrollbar();
if (scrolled_down) {
if (scrollbar.value() == scrollbar.max()) {
if (m_current_page_index < m_document->get_page_count() - 1) {
m_current_page_index++;
scrollbar.set_value(0);
}
} else {
scrollbar.set_value(scrollbar.value() + 20);
}
} else {
if (scrollbar.value() == 0) {
if (m_current_page_index > 0) {
m_current_page_index--;
scrollbar.set_value(scrollbar.max());
}
} else {
scrollbar.set_value(scrollbar.value() - 20);
}
}
}
update();
}
void PDFViewer::timer_event(Core::TimerEvent&)
{
// Clear the bitmap vector of all pages except the current page
for (size_t i = 0; i < m_rendered_page_list.size(); i++) {
if (i != m_current_page_index)
m_rendered_page_list[i].clear();
}
}
void PDFViewer::zoom_in()
{
if (m_zoom_level < number_of_zoom_levels - 1)
m_zoom_level++;
}
void PDFViewer::zoom_out()
{
if (m_zoom_level > 0)
m_zoom_level--;
}
RefPtr<Gfx::Bitmap> PDFViewer::render_page(const PDF::Page& page)
{
auto zoom_scale_factor = static_cast<float>(zoom_levels[m_zoom_level]) / 100.0f;
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 width = 300.0f * zoom_scale_factor;
float height = width * page_scale_factor;
auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, { width, height });