cut the GPU load of moving the mouse over the 3D viewport (#15674)

Co-authored-by: Rodrigo Faselli <162915171+RF47@users.noreply.github.com>

src/slic3r/GUI/SceneCache.cpp

@@ -0,0 +1,62 @@
+#include "libslic3r/libslic3r.h"
+#include "SceneCache.hpp"
+
+#include "3DScene.hpp"
+#include "GLModel.hpp"
+#include "GLShader.hpp"
+#include "GLTexture.hpp"
+#include "GUI_App.hpp"
+
+#include <glad/gl.h>
+
+namespace Slic3r {
+namespace GUI {
+
+void SceneCache::capture(Key key)
+{
+    m_valid = false;
+
+    if (wxGetApp().get_shader("flat_texture") == nullptr)
+        return;
+
+    GLTexture::copy_from_framebuffer(m_texture_id, m_texture_size, key.size[0], key.size[1], GL_NEAREST);
+
+    m_key = std::move(key);
+    m_valid = true;
+}
+
+void SceneCache::render(GLModel& quad)
+{
+    GLShaderProgram* shader = wxGetApp().get_shader("flat_texture");
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    glsafe(::glDisable(GL_BLEND));
+
+    shader->start_using();
+    shader->set_uniform("view_model_matrix", Transform3d::Identity());
+    shader->set_uniform("projection_matrix", Transform3d::Identity());
+    shader->set_uniform("uniform_texture", 0);
+
+    glsafe(::glActiveTexture(GL_TEXTURE0));
+    glsafe(::glBindTexture(GL_TEXTURE_2D, m_texture_id));
+    quad.render();
+    glsafe(::glBindTexture(GL_TEXTURE_2D, 0));
+    shader->stop_using();
+
+    glsafe(::glEnable(GL_DEPTH_TEST));
+    glsafe(::glEnable(GL_BLEND));
+    glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+}
+
+void SceneCache::reset()
+{
+    m_valid = false;
+    if (m_texture_id != 0) {
+        glsafe(::glDeleteTextures(1, &m_texture_id));
+        m_texture_id = 0;
+    }
+    m_texture_size = { { 0, 0 } };
+}
+
+} // namespace GUI
+} // namespace Slic3r