Generate labels with pangocairo (#8)

Goal of this PR is to have some basic labels generated with pangocairo
- size of the canvas should be matching the input text and grow/shrink accordingly
- basic formatting options like fontsize and align should be working

Reviewed-on: moritz/ptouch-prnt#8

src/graphics/Label.cpp

@@ -0,0 +1,229 @@
+/* 
+    ptrnt - print labels on linux
+    Copyright (C) 2023-2025  Moritz Martinius
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+ */
+
+#include "graphics/Label.hpp"
+
+#include <algorithm>
+#include <spdlog/spdlog.h>
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <vector>
+
+#include "cairo.h"
+#include "graphics/interface/ILabel.hpp"
+#include "pango/pango-font.h"
+#include "pango/pango-layout.h"
+#include "pango/pango-types.h"
+#include "pango/pangocairo.h"
+
+namespace ptprnt::graphics {
+Label::Label(const uint16_t heightPixel)
+    : mPrinterHeight(heightPixel) {
+    // Initialize resources in correct order with RAII
+    mFontMap.reset(pango_cairo_font_map_new());
+}
+
+std::vector<uint8_t> Label::getRaw() {
+    assert(mSurface != nullptr);
+    auto* surface = mSurface.get();
+
+    cairo_surface_flush(surface);
+    assert(cairo_image_surface_get_format(surface) == CAIRO_FORMAT_A8);
+
+    int width = cairo_image_surface_get_width(surface);
+    int height = cairo_image_surface_get_height(surface);
+    int stride = cairo_image_surface_get_stride(surface);
+
+    spdlog::debug("Cairo Surface data: W: {}; H: {}; S:{}", width, height, stride);
+
+    auto data = cairo_image_surface_get_data(surface);
+
+    // If stride equals width, we can return data directly
+    if (stride == width) {
+        size_t len = height * stride;
+        return {data, data + len};
+    }
+
+    // Otherwise, we need to copy row by row, removing stride padding
+    std::vector<uint8_t> result;
+    result.reserve(width * height);
+
+    for (int y = 0; y < height; ++y) {
+        uint8_t* row_start = data + (y * stride);
+        result.insert(result.end(), row_start, row_start + width);
+    }
+
+    spdlog::debug("getRaw: Removed stride padding, returning {} bytes ({}x{})", result.size(), width, height);
+    return result;
+}
+
+uint8_t Label::getNumLines(std::string_view strv) {
+    return std::count(strv.begin(), strv.end(), '\n');
+}
+
+int Label::getWidth() {
+    // Return the actual Cairo surface width (which is the layout width)
+    return mLayoutWidth;
+}
+
+int Label::getHeight() {
+    // Return the actual Cairo surface height (which is the printer height)
+    return mPrinterHeight;
+}
+
+void Label::configureLayout(PangoLayout* layout, const std::string& text, PangoFontDescription* fontDesc) {
+    pango_layout_set_font_description(layout, fontDesc);
+    pango_layout_set_text(layout, text.c_str(), static_cast<int>(text.length()));
+    pango_layout_set_height(layout, getNumLines(text) * -1);
+}
+
+void Label::applyHorizontalAlignment(PangoLayout* layout) {
+    switch (mHAlign) {
+        case HAlignPosition::LEFT:
+            pango_layout_set_alignment(layout, PANGO_ALIGN_LEFT);
+            break;
+        case HAlignPosition::RIGHT:
+            pango_layout_set_alignment(layout, PANGO_ALIGN_RIGHT);
+            break;
+        case HAlignPosition::JUSTIFY:
+            pango_layout_set_alignment(layout, PANGO_ALIGN_LEFT);
+            pango_layout_set_justify(layout, true);
+#if PANGO_VERSION_MAJOR >= 1 && PANGO_VERSION_MINOR >= 50
+            pango_layout_set_justify_last_line(layout, true);
+#endif
+            break;
+        case HAlignPosition::CENTER:
+            [[fallthrough]];
+        default:
+            pango_layout_set_alignment(layout, PANGO_ALIGN_CENTER);
+            break;
+    }
+}
+
+bool Label::create(PrintableText printableText) {
+    setFontFamily(printableText.fontFamily);
+    setFontSize(printableText.fontSize);
+
+    return create(printableText.text);
+}
+
+bool Label::create(const std::string& labelText) {
+    // TODO: we need to create a custom font config here so that Noto Emoji does not load the systems default
+    // font config here. For this, we need to create a PangoFcFontMap and a custom FcConfig
+    // see: https://docs.gtk.org/PangoFc/method.FontMap.set_config.html
+    // see: https://gist.github.com/CallumDev/7c66b3f9cf7a876ef75f
+
+    // Create a temporary surface for layout size calculations
+    auto* tempSurface = cairo_image_surface_create(CAIRO_FORMAT_A8, 1, 1);
+    auto* tempCr = cairo_create(tempSurface);
+    auto* tempPangoCtx = pango_cairo_create_context(tempCr);
+    auto* tempPangoLyt = pango_layout_new(tempPangoCtx);
+
+    PangoFontDescription* regularFont = pango_font_description_new();
+    pango_font_description_set_size(regularFont, static_cast<int>(mFontSize * PANGO_SCALE));
+    pango_font_description_set_family(regularFont, mFontFamily.c_str());
+
+    // Configure temporary layout for size calculation
+    configureLayout(tempPangoLyt, labelText, regularFont);
+    applyHorizontalAlignment(tempPangoLyt);
+
+    // Calculate label size from temporary layout
+    pango_layout_get_size(tempPangoLyt, &mLayoutWidth, &mLayoutHeight);
+    mLayoutWidth /= PANGO_SCALE;
+    mLayoutHeight /= PANGO_SCALE;
+
+    spdlog::debug("Layout width: {}, height: {}", mLayoutWidth, mLayoutHeight);
+    //auto alignedWidth = mLayoutWidth + (8 - (mLayoutWidth % 8));
+    //spdlog::debug("Aligned Layout width: {}, height: {}", alignedWidth, mLayoutHeight);
+
+    // Clean up temporary resources
+    g_object_unref(tempPangoLyt);
+    g_object_unref(tempPangoCtx);
+    cairo_destroy(tempCr);
+    cairo_surface_destroy(tempSurface);
+
+    // Now create the final surface and Pango context for actual rendering
+    mSurface.reset(cairo_image_surface_create(CAIRO_FORMAT_A8, mLayoutWidth, mPrinterHeight));
+    cairo_t* cr = cairo_create(mSurface.get());
+    mCairoCtx.reset(cr);
+    mPangoCtx.reset(pango_cairo_create_context(cr));
+    mPangoLyt.reset(pango_layout_new(mPangoCtx.get()));
+
+    // Configure final layout with same settings
+    configureLayout(mPangoLyt.get(), labelText, regularFont);
+    applyHorizontalAlignment(mPangoLyt.get());
+
+    // Adjust Cairo cursor position to respect the vertical alignment
+    switch (mVAlign) {
+        case VAlignPosition::TOP:
+            break;
+        case VAlignPosition::BOTTOM:
+            cairo_move_to(mCairoCtx.get(), 0.0, mPrinterHeight - mLayoutHeight);
+            break;
+        case VAlignPosition::MIDDLE:
+            cairo_move_to(mCairoCtx.get(), 0.0, (mPrinterHeight - mLayoutHeight) / 2);
+            break;
+        default:
+            break;
+    }
+
+    // Finally show the layout on the Cairo surface
+    pango_cairo_show_layout(mCairoCtx.get(), mPangoLyt.get());
+
+    cairo_set_source_rgb(mCairoCtx.get(), 0.0, 0.0, 0.0);
+    cairo_surface_flush(mSurface.get());
+    // mCairoCtx smart pointer will handle cleanup
+    return true;
+}
+
+void Label::writeToPng(const std::string& file) {
+    if (mSurface) {
+        cairo_surface_flush(mSurface.get());
+        cairo_surface_write_to_png(mSurface.get(), file.c_str());
+    }
+}
+
+void Label::setFontSize(const double fontSize) {
+    mFontSize = fontSize;
+}
+
+void Label::setFontFamily(const std::string& fontFamily) {
+    mFontFamily = fontFamily;
+}
+
+void Label::setHAlign(HAlignPosition hAlign) {
+    mHAlign = hAlign;
+}
+
+void Label::setVAlign(VAlignPosition vAlign) {
+    mVAlign = vAlign;
+}
+
+void Label::setText(const std::string& text) {
+    mText = text;
+}
+
+Label::~Label() {
+    spdlog::debug("Image dtor...");
+    // RAII smart pointers handle cleanup automatically
+}
+}  // namespace ptprnt::graphics