Loading screen overhaul POC

The loading screen has been significantly changed:
- The background image is now properly picked randomly instead of taking the `textures/logo.bmp` file, prepended by an external program such as Rainsted/Starter.
- The progress bar has been moved from a floating window to a thin green line at the bottom of the loading screen.
- The log window is now hidden by default. It can be turned on by setting `loadinglog` to `true` in `eu07.ini`.
- There is an animated wheel icon on the loading screen, and a trivia text is displayed.

New translation key:
- `"Did you know"`

TODO:
- Load trivia from a separate file.

scenarioloaderuilayer.cpp

@@ -0,0 +1,109 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#include "scenarioloaderuilayer.h"
+
+#include "Globals.h"
+#include "translation.h"
+
+scenarioloader_ui::scenarioloader_ui()
+{
+	m_suppress_menu = true;
+	load_random_background();
+	generate_gradient_tex();
+	load_wheel_frames();
+
+	// Temorary trivia contents
+	m_trivia.push_back("W trakcie przeprowadzonej rewizji technicznej wagonów kolejowych");
+	m_trivia.push_back("sprawdza się również daty ostatnich napraw okresowych. Wagony, dla");
+	m_trivia.push_back("których upływa termin dokonania następnej naprawy okresowej pracownik");
+	m_trivia.push_back("zespołu rewizji technicznej prowadzący oględziny winien jest przekierować");
+	m_trivia.push_back("do odpowiednich Zakładów Naprawczych Taboru Kolejowego lub wagonowni.");
+}
+
+void scenarioloader_ui::render_()
+{
+	// For some reason, ImGui windows have some padding. Offset it.
+	// TODO: Find out a way to exactly adjust the position.
+	constexpr int padding = 12;
+	ImGui::SetNextWindowPos(ImVec2(-padding, -padding));
+	ImGui::SetNextWindowSize(ImVec2(Global.window_size.x + padding * 2, Global.window_size.y + padding * 2));
+	ImGui::Begin("Neo Loading Screen", nullptr, ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoInputs | ImGuiWindowFlags_NoBackground);
+	ImDrawList* draw_list = ImGui::GetWindowDrawList();
+	ImGui::PushFont(font_loading);
+	ImGui::SetWindowFontScale(1);
+	const float font_scale_mult = 48 / ImGui::GetFontSize();
+	// Gradient at the lower half of the screen
+	const auto tex = reinterpret_cast<ImTextureID>(m_gradient_overlay_tex);
+	draw_list->AddImage(tex, ImVec2(0, Global.window_size.y / 2), ImVec2(Global.window_size.x, Global.window_size.y), ImVec2(0, 0), ImVec2(1, 1));
+	// Loading label
+	ImGui::SetWindowFontScale(font_scale_mult * 0.8);
+	draw_list->AddText(ImVec2(200, 885), IM_COL32_WHITE, m_progresstext.c_str());
+	// Loading wheel icon
+	const deferred_image* img = &m_loading_wheel_frames[38];
+	const auto loading_tex = img->get();
+	const auto loading_size = img->size();
+	draw_list->AddImage(reinterpret_cast<ImTextureID>(loading_tex), ImVec2(35, 850), ImVec2(35 + loading_size.x, 850 + loading_size.y), ImVec2(0, 0), ImVec2(1, 1));
+	// Trivia header
+	ImGui::SetWindowFontScale(font_scale_mult * 1);
+	draw_list->AddText(ImVec2(1280 - ImGui::CalcTextSize(STR_C("Did you know")).x / 2, 770), IM_COL32_WHITE, STR_C("Did you know"));
+	// Trivia content
+	ImGui::SetWindowFontScale(font_scale_mult * 0.6);
+	for (int i = 0; i < m_trivia.size(); i++)
+	{
+		std::string line = m_trivia[i];
+		draw_list->AddText(ImVec2(1280 - ImGui::CalcTextSize(line.c_str()).x / 2, 825 + i * 25), IM_COL32_WHITE, line.c_str());
+	}
+	// Progress bar at the bottom of the screen
+	const auto p1 = ImVec2(0, Global.window_size.y - 2);
+	const auto p2 = ImVec2(Global.window_size.x * m_progress, Global.window_size.y);
+	draw_list->AddRectFilled(p1, p2, ImColor(40, 210, 60, 255));
+	ImGui::PopFont();
+	ImGui::End();
+}
+
+void scenarioloader_ui::generate_gradient_tex()
+{
+	constexpr int image_width = 1;
+	constexpr int image_height = 256;
+	const auto image_data = new char[image_width * image_height * 4];
+	for (int x = 0; x < image_width; x++)
+		for (int y = 0; y < image_height; y++)
+		{
+			image_data[(y * image_width + x) * 4] = 0;
+			image_data[(y * image_width + x) * 4 + 1] = 0;
+			image_data[(y * image_width + x) * 4 + 2] = 0;
+			image_data[(y * image_width + x) * 4 + 3] = clamp(static_cast<int>(pow(y / 255.f, 0.7) * 255), 0, 255);
+		}
+
+	// Create a OpenGL texture identifier
+	GLuint image_texture;
+	glGenTextures(1, &image_texture);
+	glBindTexture(GL_TEXTURE_2D, image_texture);
+
+	// Setup filtering parameters for display
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+	// Upload pixels into texture
+	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image_width, image_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image_data);
+
+	delete[] image_data;
+
+	m_gradient_overlay_width = image_width;
+	m_gradient_overlay_height = image_height;
+	m_gradient_overlay_tex = image_texture;
+}
+
+void scenarioloader_ui::load_wheel_frames()
+{
+	for (int i = 0; i < 60; i++)
+		m_loading_wheel_frames[i] = deferred_image("ui/loading_wheel/" + std::to_string(i + 1));
+}