Added a texture cache for pango_text render output

src/display.cpp

@@ -2201,7 +2201,7 @@ void display::refresh_report(const std::string& report_name, const config * new_
 			text.set_text(t, true);
 			text.set_maximum_width(area.w);
 			text.set_maximum_height(area.h, false);
-			surface s = text.render();
+			surface s = text.render_and_get_surface();
 
 			// check if next element is text with almost no space to show it
 			const int minimal_text = 12; // width in pixels
@@ -2214,7 +2214,7 @@ void display::refresh_report(const std::string& report_name, const config * new_
 				//NOTE this space should be longer than minimal_text pixels
 				t = t + "    ";
 				text.set_text(t, true);
-				s = text.render();
+				s = text.render_and_get_surface();
 				// use the area of this element for next tooltips
 				used_ellipsis = true;
 				ellipsis_area.x = x;

src/floating_label.cpp

@@ -108,7 +108,7 @@ texture floating_label::create_texture()
 
 		renderer.set_text(text_, use_markup_);
 
-		surface& foreground = renderer.render();
+		surface& foreground = renderer.render_and_get_surface();
 
 		if(foreground == nullptr) {
 			ERR_FT << "could not create floating label's text" << std::endl;

src/font/text.cpp

@@ -33,6 +33,7 @@
 #include "preferences/general.hpp"
 
 #include <boost/algorithm/string/replace.hpp>
+#include <boost/functional/hash_fwd.hpp>
 
 #include <cassert>
 #include <cstring>
@@ -40,6 +41,9 @@
 
 namespace font {
 
+// Cache
+//pango_text_cache_t rendered_text_cache {};
+
 pango_text::pango_text()
 	: context_(pango_font_map_create_context(pango_cairo_font_map_get_default()), g_object_unref)
 	, layout_(pango_layout_new(context_.get()), g_object_unref)
@@ -65,6 +69,7 @@ pango_text::pango_text()
 	, length_(0)
 	, surface_dirty_(true)
 	, surface_buffer_()
+	, hash_(0)
 {
 	// With 72 dpi the sizes are the same as with SDL_TTF so hardcoded.
 	pango_cairo_context_set_resolution(context_.get(), 72.0);
@@ -88,13 +93,18 @@ pango_text::pango_text()
 	cairo_font_options_destroy(fo);
 }
 
-surface& pango_text::render()
+texture& pango_text::render_and_get_texture()
+{
+	this->rerender();
+	return rendered_text_cache[hash_];
+}
+
+surface& pango_text::render_and_get_surface()
 {
 	this->rerender();
 	return surface_;
 }
 
-
 int pango_text::get_width() const
 {
 	return this->get_size().x;
@@ -694,6 +704,16 @@ void pango_text::rerender(const bool force)
 		this->recalculate(force);
 		surface_dirty_ = false;
 
+		// Update hash
+		hash_ = std::hash<pango_text>()(*this);
+
+		// If we already have the appropriate texture in-cache, exit.
+		auto iter = rendered_text_cache.find(hash_);
+		if(iter != rendered_text_cache.end()) {
+			return;
+		}
+
+		// Else, render the updated text...
 		int width  = rect_.x + rect_.width;
 		int height = rect_.y + rect_.height;
 		if(maximum_width_  > 0) { width  = std::min(width, maximum_width_); }
@@ -729,6 +749,9 @@ void pango_text::rerender(const bool force)
 		surface_.assign(SDL_CreateRGBSurfaceFrom(
 			&surface_buffer_[0], width, height, 32, stride, 0x00FF0000, 0x0000FF00, 0x000000FF, 0xFF000000));
 #endif
+
+		// ...and add it to the cache.
+		rendered_text_cache.emplace(hash_, texture(surface_));
 	}
 }
 
@@ -873,3 +896,37 @@ pango_text& get_text_renderer()
 }
 
 } // namespace font
+
+namespace std
+{
+size_t hash<font::pango_text>::operator()(const font::pango_text& t) const
+{
+	using boost::hash_value;
+	using boost::hash_combine;
+
+	//
+	// Text hashing uses 32-bit FNV-1a.
+	// http://isthe.com/chongo/tech/comp/fnv/#FNV-1a
+	//
+
+	size_t hash = 2166136261;
+	for(const char& c : t.text_) {
+		hash |= c;
+		hash *= 16777619;
+	}
+
+	hash_combine(hash, t.font_class_);
+	hash_combine(hash, t.font_size_);
+	hash_combine(hash, t.font_style_);
+	hash_combine(hash, t.foreground_color_.to_rgba_bytes());
+	hash_combine(hash, t.get_width());
+	hash_combine(hash, t.get_height());
+	hash_combine(hash, t.maximum_width_);
+	hash_combine(hash, t.maximum_height_);
+	hash_combine(hash, t.alignment_);
+	hash_combine(hash, t.ellipse_mode_);
+
+	return hash;
+}
+
+} // namespace std

src/font/text.hpp

@@ -17,6 +17,7 @@
 #include "font/font_options.hpp"
 #include "color.hpp"
 #include "sdl/surface.hpp"
+#include "sdl/texture.hpp"
 #include "serialization/string_utils.hpp"
 #include "serialization/unicode_types.hpp"
 
@@ -24,19 +25,20 @@
 #include <pango/pangocairo.h>
 
 #include <functional>
+#include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
-/***
+/**
  * Note: This is the cairo-pango code path, not the SDL_TTF code path.
  */
 
 struct language_def;
 struct point;
 
-namespace font {
-
+namespace font
+{
 // add background color and also font markup.
 
 /**
@@ -82,12 +84,20 @@ public:
     pango_text & operator = (const pango_text &) = delete;
 
 	/**
-	 * Returns the rendered text.
+	 * Returns the rendered text texture from the cache.
 	 *
-	 * Before rendering it tests whether a redraw is needed and if so it first
-	 * redraws the surface before returning it.
+	 * If the surface is flagged dirty it will first be re-rendered and a new
+	 * texture added to the cache upon redraw.
 	 */
-	surface& render();
+	texture& render_and_get_texture();
+
+	/**
+	 * Returns the rendered text surface directly.
+	 *
+	 * If the surface is flagged dirty it will first be re-rendered and a new
+	 * texture added to the cache upon redraw.
+	 */
+	surface& render_and_get_surface();
 
 	/** Returns the width needed for the text. */
 	int get_width() const;
@@ -445,6 +455,12 @@ private:
 
 	std::vector<std::string> find_links(utils::string_view text) const;
 	void format_links(std::string& text, const std::vector<std::string>& links) const;
+
+	/** Hash for the current settings (text, size, etc) configuration. */
+	size_t hash_;
+
+	// Allow specialization of std::hash for pango_text
+	friend struct std::hash<pango_text>;
 };
 
 /**
@@ -456,4 +472,29 @@ private:
  */
 pango_text& get_text_renderer();
 
+using pango_text_cache_t = std::map<size_t, texture>;
+
+/**
+ * The text texture cache.
+ *
+ * Each time a specific bit of text is rendered, a corresponding texture is created and
+ * added to the cache. We don't store the surface since there isn't really any use for
+ * it. If we need texture size that can be easily queried.
+ *
+ * @todo Figure out how this can be optimized with a texture atlas. It should be possible
+ * to store smaller bits of text in the atlas and construct new textures from them.
+ */
+static pango_text_cache_t rendered_text_cache;
+
 } // namespace font
+
+// Specialize std::hash for pango_text
+namespace std
+{
+template<>
+struct hash<font::pango_text>
+{
+	size_t operator()(const font::pango_text& t) const;
+};
+
+} // namespace std

src/gui/core/canvas.cpp

@@ -1293,22 +1293,27 @@ void text_shape::draw(
 				: PANGO_ELLIPSIZE_END)
 		.set_characters_per_line(characters_per_line_);
 
-	surface& surf = text_renderer.render();
-	if(surf->w == 0) {
+	// Get the resulting texture.
+	texture& txt = text_renderer.render_and_get_texture();
+
+	// TODO: should use pango_text::get_size but the dimensions are inaccurate. Investigate.
+	texture::info info = txt.get_info();
+
+	if(info.w == 0) {
 		DBG_GUI_D << "Text: Rendering '" << text
 				  << "' resulted in an empty canvas, leave.\n";
 		return;
 	}
 
 	wfl::map_formula_callable local_variables(variables);
-	local_variables.add("text_width", wfl::variant(surf->w));
-	local_variables.add("text_height", wfl::variant(surf->h));
+	local_variables.add("text_width", wfl::variant(info.w));
+	local_variables.add("text_height", wfl::variant(info.h));
 	/*
 		std::cerr << "Text: drawing text '" << text
 			<< " maximum width " << maximum_width_(variables)
 			<< " maximum height " << maximum_height_(variables)
-			<< " text width " << surf->w
-			<< " text height " << surf->h;
+			<< " text width " << info.w
+			<< " text height " << info.h;
 	*/
 	///@todo formulas are now recalculated every draw cycle which is a
 	// bit silly unless there has been a resize. So to optimize we should
@@ -1327,25 +1332,17 @@ void text_shape::draw(
 			 _("Text doesn't start on canvas."));
 
 	// A text might be to long and will be clipped.
-	if(surf->w > static_cast<int>(w)) {
+	if(info.w > static_cast<int>(w)) {
 		WRN_GUI_D << "Text: text is too wide for the "
 					 "canvas and will be clipped.\n";
 	}
 
-	if(surf->h > static_cast<int>(h)) {
+	if(info.h > static_cast<int>(h)) {
 		WRN_GUI_D << "Text: text is too high for the "
 					 "canvas and will be clipped.\n";
 	}
 
-	SDL_Rect dst = sdl::create_rect(x, y, surf->w, surf->h);
-
-	/* NOTE: we cannot use SDL_UpdateTexture to copy the surface pixel data directly to the canvas texture
-	 * since no alpha blending occurs; values (even pure alpha) totally overwrite the underlying pixel data.
-	 *
-	 * To work around that, we create a texture from the surface and copy it to the renderer. This cleanly
-	 * copies the surface to the canvas texture with the appropriate alpha blending.
-	 */
-	texture txt(surf);
+	SDL_Rect dst = sdl::create_rect(x, y, info.w, info.h);
 
 	CVideo::get_singleton().render_copy(txt, nullptr, &dst);
 }