1 files changed, 112 insertions, 0 deletions
diff --git a/src/util/preview.cpp b/src/util/preview.cpp
new file mode 100644
index 0000000..4dd3283
--- /dev/null
+++ b/src/util/preview.cpp
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/**
+ * @file
+ * Utility functions for generating export previews.
+ */
+/* Authors:
+ *   Anshudhar Kumar Singh <anshudhar2001@gmail.com>
+ *   Martin Owens <doctormo@gmail.com>
+ *
+ * Copyright (C) 2021 Anshudhar Kumar Singh
+ *               2021 Martin Owens
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "preview.h"
+
+#include "desktop.h"
+#include "document.h"
+#include "display/cairo-utils.h"
+#include "display/drawing-context.h"
+#include "object/sp-namedview.h"
+#include "object/sp-root.h"
+#include "page-manager.h"
+
+namespace Inkscape {
+namespace UI {
+namespace PREVIEW {
+
+GdkPixbuf *render_preview(SPDocument *doc, Inkscape::Drawing &drawing, SPItem *item,
+                          unsigned width_in, unsigned height_in, Geom::OptRect *dboxIn)
+{
+    if (auto name = (item ? item->getId() : nullptr)) {
+        // Get item even if it's in another document.
+        if (item->document != doc) {
+            item = dynamic_cast<SPItem *>(doc->getObjectById(name));
+        }
+    }
+
+    Geom::OptRect dbox;
+    if (dboxIn) {
+        dbox = *dboxIn;
+    } else if (item) {
+        if (item->parent) {
+            dbox = item->documentVisualBounds();
+        } else {
+            dbox = doc->preferredBounds();
+        }
+    } else if (doc->getRoot()) {
+        // If we still dont have a dbox we will use document coordinates.
+        dbox = doc->getRoot()->documentVisualBounds();
+    }
+
+    // If we still dont have anything to render then return
+    if (!dbox) return nullptr;
+
+    // Calculate a scaling factor for the requested bounding box.
+    double sf = 1.0;
+    Geom::IntRect ibox = dbox->roundOutwards();
+    if (ibox.width() != width_in || ibox.height() != height_in) {
+        sf = std::min((double)width_in / dbox->width(),
+                      (double)height_in / dbox->height());
+        auto scaled_box = *dbox * Geom::Scale(sf);
+        ibox = scaled_box.roundOutwards();
+    }
+
+    // Resize the contents to the available space with a scale factor
+    drawing.root()->setTransform(Geom::Scale(sf));
+    drawing.update();
+
+    Geom::IntPoint pdim(width_in, height_in);
+    // The unsigned width/height can wrap around when negative.
+    int dx = ((int)width_in - ibox.width()) / 2;
+    int dy = ((int)height_in - ibox.height()) / 2;
+    Geom::IntRect area = Geom::IntRect::from_xywh(ibox.min() - Geom::IntPoint(dx, dy), pdim);
+
+    /* Actual renderable area */
+    Geom::IntRect ua = *Geom::intersect(ibox, area);
+
+    /* Render */
+    cairo_surface_t *s = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, ua.width(), ua.height());
+    Inkscape::DrawingContext dc(s, ua.min());
+    cairo_t *cr = cairo_create(s);
+    cairo_rectangle(cr, 0, 0, ua.width(), ua.height());
+
+    guint32 bg = doc->getPageManager().background_color;
+
+    // We always use checkerboard to indicate transparency.
+    if (SP_RGBA32_A_F(bg) < 1.0) {
+        auto pattern = ink_cairo_pattern_create_checkerboard(bg, false);
+        auto background = Cairo::RefPtr<Cairo::Pattern>(new Cairo::Pattern(pattern));
+        cairo_set_source(cr, background->cobj());
+        cairo_fill(cr);
+    }
+    // We always draw the background on top to indicate partial backgrounds
+    auto background = Cairo::SolidPattern::create_rgba(
+        SP_RGBA32_R_F(bg), SP_RGBA32_G_F(bg),
+        SP_RGBA32_B_F(bg), SP_RGBA32_A_F(bg));
+    cairo_set_source(cr, background->cobj());
+    cairo_fill(cr);
+
+    cairo_save(cr);
+    cairo_destroy(cr);
+
+    drawing.render(dc, ua);
+    cairo_surface_flush(s);
+    return ink_pixbuf_create_from_cairo_surface(s);
+}
+
+} // namespace PREVIEW
+} // namespace UI
+} // namespace Inkscape