Starts to implement new HTML renderer based on gumbo. Everything is a bit borked and only trivial documents work correctly.

1 files changed, 447 insertions, 0 deletions

diff --git a/src/renderers/htmlrenderer.cpp b/src/renderers/htmlrenderer.cpp
new file mode 100644
index 0000000..e1cd2da
--- /dev/null
+++ b/src/renderers/htmlrenderer.cpp
@@ -0,0 +1,447 @@
+#include "htmlrenderer.hpp"
+
+#include "renderhelpers.hpp"
+#include "textstyleinstance.hpp"
+#include "gumbo.h"
+
+#include <QDebug>
+#include <QTextTable>
+#include <QRegularExpression>
+
+static void* malloc_wrapper(void*, size_t size) { return malloc(size); }
+
+static void free_wrapper(void*, void* ptr) { free(ptr); }
+
+static GumboOptions const gumbo_options = {
+    &malloc_wrapper, &free_wrapper, // memory management
+    nullptr,                        // user pointer
+    4,                              // tab width
+    false,                          // stop on first error
+    -1,                             // maximum numbers of errors (-1 = infinite)
+    GUMBO_TAG_LAST,
+    GUMBO_NAMESPACE_HTML
+};
+
+static void destroyGumboOutput(GumboOutput * output)
+{
+    gumbo_destroy_output(&gumbo_options, output);
+}
+
+static const char* find_title(const GumboNode* root) {
+    assert(root->type == GUMBO_NODE_ELEMENT);
+    if(root->v.element.children.length < 2)
+        return nullptr;
+
+    const GumboVector* root_children = &root->v.element.children;
+    GumboNode* head = nullptr;
+    for (size_t i = 0; i < root_children->length; ++i) {
+        GumboNode* child = (GumboNode*)root_children->data[i];
+        if (child->type == GUMBO_NODE_ELEMENT and child->v.element.tag == GUMBO_TAG_HEAD) {
+            head = child;
+            break;
+        }
+    }
+    if(head == nullptr)
+        return nullptr;
+
+    GumboVector* head_children = &head->v.element.children;
+    for (size_t i = 0; i < head_children->length; ++i) {
+        GumboNode* child = (GumboNode*)head_children->data[i];
+        if (child->type == GUMBO_NODE_ELEMENT and child->v.element.tag == GUMBO_TAG_TITLE) {
+            if (child->v.element.children.length != 1) {
+                return "";
+            }
+            GumboNode* title_text = (GumboNode*)child->v.element.children.data[0];
+            if(title_text->type == GUMBO_NODE_TEXT or title_text->type == GUMBO_NODE_WHITESPACE)
+                return title_text->v.text.text;
+            return nullptr;
+        }
+    }
+    return nullptr;
+}
+
+struct RenderState
+{
+    QTextCursor cursor;
+    TextStyleInstance text_style;
+    QUrl root_url;
+    DocumentStyle const * style;
+    DocumentOutlineModel * outline;
+};
+
+static char const * getAttribute(GumboElement const & element, char const * attrib_name)
+{
+    for(size_t i = 0; i < element.attributes.length; i++)
+    {
+        auto const attrib = static_cast<GumboAttribute const *>(element.attributes.data[i]);
+        if(strcmp(attrib->name, attrib_name) == 0)
+            return attrib->value;
+    }
+    return nullptr;
+}
+
+struct TextFormatReset
+{
+    QTextCursor * cursor;
+
+    QTextCharFormat char_format;
+    QTextBlockFormat block_format;
+
+    TextFormatReset(QTextCursor * cursor) :
+        cursor(cursor),
+        char_format(cursor->charFormat()),
+        block_format(cursor->blockFormat())
+    {
+
+    }
+
+    TextFormatReset(TextFormatReset const &) = delete;
+    TextFormatReset(TextFormatReset &&) = delete;
+
+    ~TextFormatReset()
+    {
+        this->cursor->setCharFormat(this->char_format);
+        this->cursor->setBlockFormat(this->block_format);
+    }
+
+};
+
+// Problems:
+// Style/theme elements must use a push/pop
+// use instead of "replacing" styles
+// Otherwise, <h1><a>Foo</a></h1> will be rendered as a link, not as a heading.
+// Should be combined here.
+
+static void renderRecursive(RenderState & state, GumboNode const & node, int nesting = 0)
+{
+    auto & cursor = state.cursor;
+    auto & text_style = state.text_style;
+    switch(node.type)
+    {
+    /** Document node.  v will be a GumboDocument. */
+    case GUMBO_NODE_DOCUMENT: {
+        qWarning() << "Detected embedded document";
+    }
+
+    /** Element node.  v will be a GumboElement. */
+    case GUMBO_NODE_ELEMENT: {
+        auto const & element = node.v.element;
+
+        TextFormatReset format_reset { &cursor };
+
+        // qDebug() << "begin node(" << gumbo_normalized_tagname(element.tag) << ")";
+
+        switch(element.tag) {
+
+        // Stripped tags
+        case GUMBO_TAG_STYLE:
+        case GUMBO_TAG_SCRIPT:
+            return;
+
+        case GUMBO_TAG_NAV: {
+            // TODO: Optionally strip navigation from sites
+            if(true)
+                return;
+            break;
+        }
+
+        // Terminal tags
+        case GUMBO_TAG_IMG: {
+            // TODO: Insert link to image here
+            cursor.insertText("[IMG]");
+            return;
+        }
+        case GUMBO_TAG_SVG: {
+            // TODO: Insert link to image here
+            cursor.insertText("[SVG]");
+            return;
+        }
+        case GUMBO_TAG_BUTTON: {
+            // TODO: Insert link to image here
+            cursor.insertText("[BUTTON]");
+            return;
+        }
+        case GUMBO_TAG_INPUT: {
+            // TODO: Insert link to image here
+            cursor.insertText("[INPUT]");
+            return;
+        }
+
+        // Paragraph-like elements:
+        case GUMBO_TAG_DIV: // <div> is the same as <p> for us
+        case GUMBO_TAG_P: {
+            // cursor.insertBlock();
+            break;
+        }
+        case GUMBO_TAG_H1: {
+            // cursor.insertBlock();
+            cursor.setBlockFormat(text_style.heading_format);
+            cursor.setCharFormat(text_style.standard_h1);
+            break;
+        }
+        case GUMBO_TAG_H2: {
+            // cursor.insertBlock();
+            cursor.setBlockFormat(text_style.heading_format);
+            cursor.setCharFormat(text_style.standard_h2);
+
+            break;
+        }
+        case GUMBO_TAG_H3: {
+            // cursor.insertBlock();
+            cursor.setBlockFormat(text_style.heading_format);
+            cursor.setCharFormat(text_style.standard_h3);
+            break;
+        }
+
+        case GUMBO_TAG_PRE: {
+            // cursor.insertBlock();
+            cursor.setBlockFormat(text_style.preformatted_format);
+            cursor.setCharFormat(text_style.preformatted);
+            break;
+        }
+
+        case GUMBO_TAG_OL:
+        case GUMBO_TAG_UL: {
+            // cursor.insertBlock();
+
+            if(element.tag == GUMBO_TAG_OL) {
+                auto fmt = text_style.list_format;
+                fmt.setStyle(QTextListFormat::ListDecimal);
+                fmt.setNumberPrefix("");
+                fmt.setNumberSuffix(".");
+                cursor.createList(fmt);
+            }
+            else {
+                cursor.createList(text_style.list_format);
+            }
+            break;
+        }
+        case GUMBO_TAG_LI: {
+            break;
+        }
+
+
+        // Text modification elements:
+        case GUMBO_TAG_SPAN: {
+            // This usually has a style change, but we ignore that completly
+            break;
+        }
+        case GUMBO_TAG_BR: {
+            cursor.insertText("\n");
+            break;
+        }
+        case GUMBO_TAG_I: {
+            auto fmt = cursor.charFormat();
+            fmt.setFontItalic(true);
+            cursor.setCharFormat(fmt);
+            break;
+        }
+        case GUMBO_TAG_B: {
+            auto fmt = cursor.charFormat();
+            fmt.setFontWeight(QFont::Bold);
+            cursor.setCharFormat(fmt);
+            break;
+        }
+        case GUMBO_TAG_U: {
+            auto fmt = cursor.charFormat();
+            fmt.setFontUnderline(true);
+            cursor.setCharFormat(fmt);
+            break;
+        }
+        case GUMBO_TAG_A: {
+            char const * anchor = getAttribute(element, "href");
+            if(anchor == nullptr) {
+                anchor = "#";
+            }
+
+            auto fmt = text_style.standard_link;
+            fmt.setAnchor(true);
+            fmt.setAnchorHref(QString::fromUtf8(anchor));
+            cursor.setBlockFormat(text_style.link_format);
+            cursor.setCharFormat(fmt);
+            break;
+        }
+        case GUMBO_TAG_BLOCKQUOTE: {
+            QTextTable *table = cursor.insertTable(1, 1,text_style.blockquote_tableformat);
+            cursor.setBlockFormat(text_style.blockquote_format);
+            QTextTableCell cell = table->cellAt(0, 0);
+            cell.setFormat(text_style.blockquote);
+
+            cursor.setCharFormat(text_style.blockquote);
+
+            break;
+        }
+        default:
+            qDebug() << "unhandled tag:" << gumbo_normalized_tagname(element.tag);
+            break;
+        }
+
+        for (size_t i = 0; i < element.children.length; ++i) {
+            GumboNode* child = (GumboNode*)element.children.data[i];
+            renderRecursive(state, *child, nesting + 1);
+        }
+
+        switch(element.tag) {
+        // case GUMBO_TAG_PRE: {
+//            // Set the last line of the preformatted block to have
+//            // standard line height.
+//            QTextBlockFormat fmt = cursor.blockFormat();
+//            fmt.setLineHeight(state.style->line_height_p, QTextBlockFormat::LineDistanceHeight);
+//            cursor.movePosition(QTextCursor::PreviousBlock);
+//            cursor.setBlockFormat(fmt);
+
+//            cursor.movePosition(QTextCursor::NextBlock);
+//            break;
+//        }
+
+        // Requires closing block
+        case GUMBO_TAG_PRE:
+        case GUMBO_TAG_P:
+        case GUMBO_TAG_DIV:
+        case GUMBO_TAG_H1:
+        case GUMBO_TAG_H2:
+        case GUMBO_TAG_H3:
+            cursor.insertBlock();
+            break;
+
+        case GUMBO_TAG_OL:
+        case GUMBO_TAG_UL:
+            // cursor.insertBlock();
+            break;
+
+        case GUMBO_TAG_LI:
+            // Terminate the <li> by pressing "enter"
+            cursor.insertBlock();
+            break;
+
+        case GUMBO_TAG_BLOCKQUOTE:
+            cursor.deletePreviousChar();
+            cursor.movePosition(QTextCursor::NextBlock);
+            break;
+
+        default: break;
+        }
+
+        // qDebug() << "end node(" << gumbo_normalized_tagname(element.tag) << ")";
+
+        break;
+    }
+
+    /** Text node.  v will be a GumboText. */
+    case GUMBO_NODE_TEXT: {
+        auto const & text = node.v.text;
+
+        auto contents = QString::fromUtf8(text.text);
+        // qDebug() << contents;
+
+        QRegularExpression regex { "\\s+", QRegularExpression::DotMatchesEverythingOption };
+
+        // TODO: This is not quite right, but QTextCursor::inserText
+        // will insert spurious blocks when a "\n" is encountered.
+        state.cursor.insertText(contents.replace(regex, " "));
+        break;
+    }
+
+    /** CDATA node. v will be a GumboText. */
+    case GUMBO_NODE_CDATA: {
+        auto const & text = node.v.text;
+
+        auto const contents = QString::fromUtf8(text.text);
+
+        // TODO: This is not quite right, but QTextCursor::inserText
+        // will insert spurious blocks when a "\n" is encountered.
+        state.cursor.insertText(contents.trimmed());
+        break;
+    }
+
+    /** Comment node.  v will be a GumboText, excluding comment delimiters. */
+    case GUMBO_NODE_COMMENT: {
+        // qDebug() << "comment(" << ")";
+        break;
+    }
+
+    /** Text node, where all contents is whitespace.  v will be a GumboText. */
+    case GUMBO_NODE_WHITESPACE: {
+        // qDebug() << "whitespace(" << ")";
+        break;
+    }
+
+    /** Template node.  This is separate from GUMBO_NODE_ELEMENT because many
+     * client libraries will want to ignore the contents of template nodes, as
+     * the spec suggests.  Recursing on GUMBO_NODE_ELEMENT will do the right thing
+     * here, while clients that want to include template contents should also
+     * check for GUMBO_NODE_TEMPLATE.  v will be a GumboElement.  */
+    case GUMBO_NODE_TEMPLATE: {
+        qDebug() << "template(" << "???" << ")";
+        break;
+    }
+    }
+}
+
+std::unique_ptr<QTextDocument> HtmlRenderer::render(
+        QByteArray const &input,
+        QUrl const & root_url,
+        DocumentStyle const & style,
+        DocumentOutlineModel & outline,
+        QString & page_title)
+{
+    std::unique_ptr<GumboOutput, decltype(&destroyGumboOutput)> gumbo_output {
+        gumbo_parse_with_options(&gumbo_options, input.data(), input.length()),
+        &destroyGumboOutput,
+    };
+
+    if(gumbo_output->errors.length > 0) {
+        qDebug() << "Parsing the html document yielded" << gumbo_output->errors.length << "errors!";
+    }
+
+    if(gumbo_output->root->type != GUMBO_NODE_ELEMENT) {
+        qWarning() << "html document has no proper root node!";
+        return nullptr;
+    }
+
+    auto doc = std::make_unique<QTextDocument>();
+    renderhelpers::setPageMargins(doc.get(), style.margin_h, style.margin_v);
+    doc->setIndentWidth(style.indent_size);
+
+    outline.beginBuild();
+
+    // Find page title
+    {
+        const char* title = find_title(gumbo_output->root);
+        if(title != nullptr) {
+            page_title = QString::fromUtf8(title);
+        }
+    }
+
+    {
+        GumboVector const * const root_children = &gumbo_output->root->v.element.children;
+        GumboNode* body = nullptr;
+        for (size_t i = 0; i < root_children->length; ++i) {
+            GumboNode* child = (GumboNode*)root_children->data[i];
+            if (child->type == GUMBO_NODE_ELEMENT and child->v.element.tag == GUMBO_TAG_BODY) {
+                body = child;
+                break;
+            }
+        }
+        if(body != nullptr)
+        {
+            RenderState state {
+                QTextCursor { doc.get() },
+                TextStyleInstance { style },
+                root_url,
+                &style,
+                &outline,
+            };
+
+            state.cursor.setBlockFormat(state.text_style.standard_format);
+            state.cursor.setCharFormat(state.text_style.standard);
+
+            renderRecursive(state, *body);
+        }
+    }
+
+
+    outline.endBuild();
+
+    return doc;
+}