More info for user in preview of font in combo box.

+ Clear rest of texture when short text is used

src/slic3r/GUI/Gizmos/GLGizmoEmboss.cpp

@@ -1768,33 +1768,46 @@ void GLGizmoEmboss::init_font_name_texture() {
 
 void GLGizmoEmboss::draw_font_preview(FaceName& face, bool is_visible)
 {
+    // Limit for opened font files at one moment
     unsigned int &count_opened_fonts = m_face_names.count_opened_font_files; 
+    // Size of texture
     ImVec2 size(m_gui_cfg->face_name_size.x(), m_gui_cfg->face_name_size.y());
-    // set to pixel 0,0 in texture
+    float  count_cached_textures_f = static_cast<float>(m_face_names.count_cached_textures);
-    ImVec2      uv0(0.f, 0.f), uv1(1.f / size.x, 1.f / size.y / m_face_names.count_cached_textures);
+    std::string state_text;
-    ImTextureID tex_id = (void *) (intptr_t) m_face_names.texture_id;
+    // uv0 and uv1 set to pixel 0,0 in texture
+    ImVec2 uv0(0.f, 0.f), uv1(1.f / size.x, 1.f / size.y / count_cached_textures_f);
     if (face.is_created != nullptr) {
+        // not created preview 
         if (*face.is_created) {
+            // Already created preview
             size_t texture_index = face.texture_index;
-            uv0                  = ImVec2(0.f, texture_index / (float) m_face_names.count_cached_textures),
+            uv0 = ImVec2(0.f, texture_index / count_cached_textures_f);
-            uv1                  = ImVec2(1.f, (texture_index + 1) / (float) m_face_names.count_cached_textures);
+            uv1 = ImVec2(1.f, (texture_index + 1) / count_cached_textures_f);
-        } else if (!is_visible) {
+        } else {
+            // Not finished preview
+            if (is_visible) {
+                // when not canceled still loading
+                state_text = (face.cancel->load())? 
+                    _u8L(" No symbol"):
+                    _u8L(" ... Loading");                
+            } else {
+                // not finished and not visible cancel job
                 face.is_created = nullptr;
                 face.cancel->store(true);
             }
+        }
     } else if (is_visible && count_opened_fonts < m_gui_cfg->max_count_opened_font_files) {
         ++count_opened_fonts;
         face.cancel     = std::make_shared<std::atomic_bool>(false);
         face.is_created = std::make_shared<bool>(false);
 
-        std::string text = m_text.empty() ? "AaBbCc" : m_text;
-
         const unsigned char gray_level = 5;
         // format type and level must match to texture data
         const GLenum format = GL_RGBA, type = GL_UNSIGNED_BYTE;
         const GLint  level = 0;
         // select next texture index
         size_t texture_index = (m_face_names.texture_index + 1) % m_face_names.count_cached_textures;
+
         // set previous cach as deleted
         for (FaceName &f : m_face_names.faces)
             if (f.texture_index == texture_index) {
@@ -1805,12 +1818,9 @@ void GLGizmoEmboss::draw_font_preview(FaceName& face, bool is_visible)
         m_face_names.texture_index = texture_index;
         face.texture_index         = texture_index;
 
-        // clear texture
-
-
         // render text to texture
         FontImageData data{
-            text,
+            m_text,
             face.wx_name,
             m_face_names.encoding,
             m_face_names.texture_id,
@@ -1827,9 +1837,18 @@ void GLGizmoEmboss::draw_font_preview(FaceName& face, bool is_visible)
         auto  job    = std::make_unique<CreateFontImageJob>(std::move(data));
         auto &worker = wxGetApp().plater()->get_ui_job_worker();
         queue_job(worker, std::move(job));
+    } else {
+        // cant start new thread at this moment so wait in queue
+        state_text = _u8L(" ... In queue");
+    }
+
+    if (!state_text.empty()) {
+        ImGui::SameLine(m_gui_cfg->face_name_texture_offset_x);
+        m_imgui->text(state_text);
     }
 
     ImGui::SameLine(m_gui_cfg->face_name_texture_offset_x);
+    ImTextureID tex_id = (void *) (intptr_t) m_face_names.texture_id;
     ImGui::Image(tex_id, size, uv0, uv1);
 }
 
@@ -2674,7 +2693,6 @@ void GLGizmoEmboss::draw_style_edit() {
         ImGui::TextColored(ImGuiWrapper::COL_ORANGE_DARK, "%s", _u8L("WxFont is not loaded properly.").c_str());
         return;
     }
-
     bool exist_stored_style = m_style_manager.exist_stored_style();
     bool exist_change_in_font = is_font_changed(m_style_manager);
     const GuiCfg::Translations &tr = m_gui_cfg->translations;

src/slic3r/GUI/Gizmos/GLGizmoEmboss.hpp

@@ -258,6 +258,7 @@ private:
                 
         // protection for open too much font files together
         // Gtk:ERROR:../../../../gtk/gtkiconhelper.c:494:ensure_surface_for_gicon: assertion failed (error == NULL): Failed to load /usr/share/icons/Yaru/48x48/status/image-missing.png: Error opening file /usr/share/icons/Yaru/48x48/status/image-missing.png: Too many open files (g-io-error-quark, 31)
+        // This variable must exist until no CreateFontImageJob is running
         unsigned int count_opened_font_files = 0; 
 
         // Configuration for texture height

src/slic3r/GUI/Jobs/CreateFontNameImageJob.cpp

@@ -19,10 +19,11 @@
 using namespace Slic3r;
 using namespace Slic3r::GUI;
 
+const std::string CreateFontImageJob::default_text = "AaBbCc 123";
+
 CreateFontImageJob::CreateFontImageJob(FontImageData &&input)
     : m_input(std::move(input))
 {
-    assert(!m_input.text.empty());
     assert(wxFontEnumerator::IsValidFacename(m_input.font_name));
     assert(m_input.gray_level > 0 && m_input.gray_level < 255);
     assert(m_input.texture_id != 0);
@@ -41,9 +42,11 @@ void CreateFontImageJob::process(Ctl &ctl)
     if (font_file == nullptr) return;
 
     Emboss::FontFileWithCache font_file_with_cache(std::move(font_file));
-    FontProp                  fp;
     // use only first line of text
-    std::string text = m_input.text;
+    std::string& text = m_input.text;
+    if (text.empty())
+        text = default_text; // copy
+
     size_t enter_pos = text.find('\n');
     if (enter_pos < text.size()) {
         // text start with enter
@@ -57,12 +60,26 @@ void CreateFontImageJob::process(Ctl &ctl)
         if (cancel->load()) return true;
         return false; 
     };
+
+    FontProp fp; // create default font parameters
     ExPolygons shapes = Emboss::text2shapes(font_file_with_cache, text.c_str(), fp, was_canceled);
+
+    // select some character from font e.g. default text
+    if (shapes.empty())
+        shapes = Emboss::text2shapes(font_file_with_cache, default_text.c_str(), fp, was_canceled);
+    if (shapes.empty()) {
+        m_input.cancel->store(true);
+        return;
+    }
+
     // normalize height of font
     BoundingBox bounding_box;
     for (ExPolygon &shape : shapes)
         bounding_box.merge(BoundingBox(shape.contour.points));
-    if (bounding_box.size().x() < 1 || bounding_box.size().y() < 1) return;
+    if (bounding_box.size().x() < 1 || bounding_box.size().y() < 1) {
+        m_input.cancel->store(true);
+        return;
+    }
     double scale = m_input.size.y() / (double) bounding_box.size().y();
     BoundingBoxf bb2(bounding_box.min.cast<double>(),
                      bounding_box.max.cast<double>());
@@ -74,7 +91,8 @@ void CreateFontImageJob::process(Ctl &ctl)
     if (m_tex_size.y() > m_input.size.y()) m_tex_size.y() = m_input.size.y();
 
     // Set up result
-    m_result = std::vector<unsigned char>(m_tex_size.x() * m_tex_size.y() * 4, {255});
+    unsigned bit_count = 4; // RGBA
+    m_result = std::vector<unsigned char>(m_tex_size.x() * m_tex_size.y() * bit_count, {255});
 
     sla::Resolution resolution(m_tex_size.x(), m_tex_size.y());
     double pixel_dim = SCALING_FACTOR / scale;
@@ -123,13 +141,17 @@ void CreateFontImageJob::finalize(bool canceled, std::exception_ptr &)
     const GLenum target = GL_TEXTURE_2D;
     glsafe(::glBindTexture(target, m_input.texture_id));
 
-    GLint 
+    GLsizei w = m_tex_size.x(), h = m_tex_size.y();
-        w = m_tex_size.x(), h = m_tex_size.y(),
+    GLint xoffset = m_input.size.x() - m_tex_size.x(), // arrange right
-        xoffset = m_input.size.x() - m_tex_size.x(), // arrange right
           yoffset = m_input.size.y() * m_input.index;
     glsafe(::glTexSubImage2D(target, m_input.level, xoffset, yoffset, w, h,
                              m_input.format, m_input.type, m_result.data()));
 
+    // clear rest of texture
+    std::vector<unsigned char> empty_data(xoffset * h * 4, {0});
+    glsafe(::glTexSubImage2D(target, m_input.level, 0, yoffset, xoffset, h,
+                             m_input.format, m_input.type, empty_data.data()));
+
     // bind default texture
     GLuint no_texture_id = 0;
     glsafe(::glBindTexture(target, no_texture_id));

src/slic3r/GUI/Jobs/CreateFontNameImageJob.hpp

@@ -68,6 +68,12 @@ public:
     /// <param name="canceled"></param>
     /// <param name=""></param>
     void finalize(bool canceled, std::exception_ptr &) override;
+
+    /// <summary>
+    /// Text used for generate preview for empty text
+    /// and when no glyph for given m_input.text
+    /// </summary>
+    static const std::string default_text;
 };
 
 } // namespace Slic3r::GUI