Use host-visible buffers for text rendering

Remove text caching logic and m_lastRenderedText. Switch to direct
memory-mapped updates of dynamic vertex and index buffers each frame,
eliminating staging/caching paths and simplifying debug/update logic.

src/vulkanrenderer.cpp

@@ -2663,35 +2663,7 @@ void VulkanRenderer::drawText(VkCommandBuffer commandBuffer, int frameCount,
         return; // Text rendering not available
     }
 
-    // 构建当前帧的文本内容（用于缓存比较）
+    // 使用 host-visible buffers 后，每帧更新成本很低（只是 memcpy），无需缓存
-    std::string currentText = lockInfo + "|" + std::to_string(paintingEnabled) + "|" 
-                            + std::to_string(m_width) + "x" + std::to_string(m_height);
-    
-    // 检查文本是否变化，只在变化时重建 buffers
-    bool needsRebuild = (currentText != m_lastRenderedText) || (m_textVertexBuffer == VK_NULL_HANDLE);
-    
-    // 如果文本没有变化且 buffers 已存在，直接使用缓存的 buffers
-    if (!needsRebuild && m_textVertexBuffer != VK_NULL_HANDLE && m_textIndexBuffer != VK_NULL_HANDLE) {
-        // Bind text pipeline
-        vkCmdBindPipeline(commandBuffer, VK_PIPELINE_BIND_POINT_GRAPHICS, m_textPipeline);
-
-        // Bind descriptor sets for text rendering (if using textures)
-        if (!m_descriptorSets.empty()) {
-            vkCmdBindDescriptorSets(commandBuffer, VK_PIPELINE_BIND_POINT_GRAPHICS,
-                                   m_textPipelineLayout, 0, 1,
-                                   &m_descriptorSets[0], 0, nullptr);
-        }
-
-        // Draw text using cached buffers
-        VkBuffer vertexBuffers[] = {m_textVertexBuffer};
-        VkDeviceSize offsets[] = {0};
-        vkCmdBindVertexBuffers(commandBuffer, 0, 1, vertexBuffers, offsets);
-        vkCmdBindIndexBuffer(commandBuffer, m_textIndexBuffer, 0, VK_INDEX_TYPE_UINT16);
-        vkCmdDrawIndexed(commandBuffer, m_textIndexCount, 1, 0, 0, 0);
-        return;
-    }
-
-    // 文本变化了，需要重建 buffers
 
     // Bind text pipeline
     vkCmdBindPipeline(commandBuffer, VK_PIPELINE_BIND_POINT_GRAPHICS, m_textPipeline);
@@ -2808,7 +2780,7 @@ void VulkanRenderer::drawText(VkCommandBuffer commandBuffer, int frameCount,
         return;
     }
 
-    if (textDebugCounter % 300 == 1 || needsRebuild) {
+    if (textDebugCounter % 300 == 1) {
         std::cout << "Drawing text with " << vertices.size() << " vertices, "
                   << indices.size() << " indices" << std::endl;
         std::cout << "Window size: " << m_width << "x" << m_height << std::endl;
@@ -2826,7 +2798,6 @@ void VulkanRenderer::drawText(VkCommandBuffer commandBuffer, int frameCount,
         
         if (!createDynamicVertexBuffer(textVertexSize, m_textVertexBuffer, m_textVertexMemory)) {
             logError("Failed to create dynamic text vertex buffer");
-            m_lastRenderedText.clear();
             return;
         }
         if (!createDynamicIndexBuffer(textIndexSize, m_textIndexBuffer, m_textIndexMemory)) {
@@ -2835,29 +2806,26 @@ void VulkanRenderer::drawText(VkCommandBuffer commandBuffer, int frameCount,
             vkFreeMemory(m_device, m_textVertexMemory, nullptr);
             m_textVertexBuffer = VK_NULL_HANDLE;
             m_textVertexMemory = VK_NULL_HANDLE;
-            m_lastRenderedText.clear();
             return;
         }
         
         std::cout << "Dynamic text buffers created (host-visible, no staging)" << std::endl;
     }
 
-    // 直接更新 buffer 内容（通过内存映射，无需命令队列）
+    // 每帧直接更新 buffer 内容（通过内存映射，无需命令队列）
+    // 使用 host-visible buffers 后，更新成本极低，无需缓存
     if (!vertices.empty() && !indices.empty()) {
         if (!updateDynamicBuffer(m_textVertexMemory, vertices.data(), 
                                 sizeof(Vertex) * vertices.size())) {
             logError("Failed to update text vertex buffer");
-            m_lastRenderedText.clear();
             return;
         }
         if (!updateDynamicBuffer(m_textIndexMemory, indices.data(),
                                 sizeof(uint16_t) * indices.size())) {
             logError("Failed to update text index buffer");
-            m_lastRenderedText.clear();
             return;
         }
         m_textIndexCount = indices.size();
-        m_lastRenderedText = currentText; // 缓存当前文本内容
     }
 
     // Draw text with newly created buffers

src/vulkanrenderer.h

@@ -384,8 +384,7 @@ private:
     VkSampler m_fontSampler;
     std::map<char, CharInfo> m_charInfoMap;
     
-    // 文本缓存，避免每帧重建 text buffers
+    // 文本动态 buffers（host-visible，每帧直接映射更新）
-    std::string m_lastRenderedText;
     VkBuffer m_textVertexBuffer;
     VkDeviceMemory m_textVertexMemory;
     VkBuffer m_textIndexBuffer;